Characterization of MeV ion -implanted GaInAs/GaAsusing x -ray and Raman techniques

Chu R. Wie, K. Xie, H.M. Kim, and J.F. ChenState University of New York at Buffallo, Dept. of ECE, Amherst, New York 14260

G. Burns, F. H. Dacol, G.D. Pettit, and J.M. WoodallIBM T.J. Watson Res. Ctr., Yorktown Heights, New York 10598

ABSTRACT

Lattice relaxation, elastic strain, and phonon shifts are studied in as- grown, MeV ion -implanted, andthermally annealed strained GainAs layers on GaAs(001) substrates. The degree of lattice relaxation forthe as -grown samples is discussed in terms of the measured in -plane lattice constants and thecalculated critical thickness. For the 15 MeV Cl or 9 MeV P ion bombarded GaInAs /GaAs, thebeam -induced elastic strains and beam- induced phonon shifts are measured and discussed for sampleswith different degrees of initial relaxation. Thermal annealing on the as -grown and the ion -implantedGainAs layers indicates a substantial thermal loss of indium in the thin surface layers and a fullrecovery of radiation damage in the GaInAs layers by 500 °C.

1. INTRODUCTION

Nondestructive characterization of material or device properties is of great importance in semiconductorresearch because it allows different physical properties to be studied in correlation. The x -ray rocking curvetechnique and Raman technique can provide information nondestructively. These two techniques have been usedto study heterojunction epitaxial films, superlattices2, ion -implanted bulk semiconductors3, MeV ion bombarded

bulk III -V compounds4'5, and MeV ion -bombarded strained epitaxial films6. X -ray rocking curves (XRC) measurethe lattice spacings of a film relative to the subtrate, in the direction normal to the surface and in two in -planedirections. From the lattice spacings, the elastic strains can be calculated under the assumption that a biaxialstress exists in the film. The film composition of ternary epitaxial layers can also be calculated under the sameassumption. For partially relaxed strained epitaxial layers such as GalnAs/GaAs and GaAs/Si, average spacingsof the misfit dislocations can be calculated from the XRC data if one knows the dislocation type. It has beenrepoted that misfit dislocations at the heterojunction interfaces of zincblende crystals are 60 degreedislocations?. The layer thickness can also be obtained from the XRC data if the rocking curves are fitted with asimulated curve calculated using an x -ray diffraction theory8.

The phonon frequencies are shifted in the presence of elastic strains. The stress- induced shifts offirst -order Raman frequencies have been measured for diamond- and zincblende -type semiconductors and thephonon deformation constants were calculated from the measured shifts9. Recently, using these deformation

constants the Raman technique was used to find the elastic strains in a Si film on SiO2 formed by

ion -implantations° and the strains at the surfaces of polished GaAs(100) and InP(100) crystalsi'. Thebulk -equivalent k =0, LO phonon frequencies in GaInAs ternary alloy films on GaAs substrates were measured bysubtracting the strain -induced part from the measured phonon frequencies1. The strain -induced term is

calculated using the elastic strains measured by XRC and the phonon defromation constants1.

Since the penetration depth of the laser beam (wavelength= 514.5 nm) used in these Raman measurements is -100 nm and that of the x -ray beam used in XRC is several pm, the Raman technique is more sensitive to the thinsurface layers where as the XRC technique gives an average value over each layer in the heterostructure (if thetotal thickness is below the penetration depth of the x -ray beam). For ion -damaged epitaxial layers, these two

SPIE Vol 946 Spectroscopic Characterization Techniques for Semiconductor Technology Ill (1988) / 155

Characterization of MeV ion-implanted GalnAs/GaAs using x-ray and Raman techniques

Chu R. Wie, K. Xie, H.M. Kirn, and J.F. Chen State University of New York at Buffallo, Dept. of ECE, Amherst, New York 14260

G. Burns, F. H. Dacol, G.D. Pettit, and J.M. Woodall IBM TJ. Watson Res. Ctr., Yorktown Heights, New York 10598

ABSTRACT

Lattice relaxation, elastic strain, and phonon shifts are studied in as-grown, MeV ion-implanted, and thermally annealed strained GalnAs layers on GaAs(OOl) substrates. The degree of lattice relaxation for the as-grown samples is discussed in terms of the measured in-plane lattice constants and the calculated critical thickness. For the 15 MeV Cl or 9 MeV P ion bombarded GalnAs/GaAs, the beam-induced elastic strains and beam-induced phonon shifts are measured and discussed for samples with different degrees of initial relaxation. Thermal annealing on the as-grown and the ion-implanted GalnAs layers indicates a substantial thermal loss of indium in the thin surface layers and a full recovery of radiation damage in the GalnAs layers by 500 °C.

1. INTRODUCTION

Nondestructive characterization of material or device properties is of great importance in semiconductor research because it allows different physical properties to be studied in correlation. The x-ray rocking curve technique and Raman technique can provide information nondestructively. These two techniques have been used to study heterojunction epitaxial films 1 , superlattices 2 , ion-implanted bulk semiconductors 3, MeV ion bombarded bulk ni-V compounds 4 ' 5 , and MeV ion-bombarded strained epitaxial films 6 . X-ray rocking curves (XRC) measure the lattice spacings of a film relative to the subtrate, in the direction normal to the surface and in two in-plane directions. From the lattice spacings, the elastic strains can be calculated under the assumption that a biaxial stress exists in the film. The film composition of ternary epitaxial layers can also be calculated under the same assumption. For partially relaxed strained epitaxial layers such as GalnAs/GaAs and GaAs/Si, average spacings of the misfit dislocations can be calculated from the XRC data if one knows the dislocation type. It has been repoted that misfit dislocations at the heterojunction interfaces of zincblende crystals are 60 degree dislocations^7 . The layer thickness can also be obtained from the XRC data if the rocking curves are fitted with a simulated curve calculated using an x-ray diffraction theory8 .

The phonon frequencies are shifted in the presence of elastic strains. The stress-induced shifts of first-order Raman frequencies have been measured for diamond- and zincblende-type semiconductors and the phonon deformation constants were calculated from the measured shifts 9 . Recently, using these deformation constants the Raman technique was used to find the elastic strains in a Si film on SiO£ formed by ion-implantation 10 and the strains at the surfaces of polished GaAs(lOO) and InP(lOO) crystals 11 . The bulk-equivalent k=0, LO phonon frequencies in GalnAs ternary alloy films on GaAs substrates were measured by subtracting the strain-induced part from the measured phonon frequencies 1 . The strain-induced term is calculated using the elastic strains measured by XRC and the phonon defromation constants 1 .

Since the penetration depth of the laser beam (wavelength= 514.5 nm) used in these Raman measurements is ~ 100 nm and that of the x-ray beam used in XRC is several Jim, the Raman technique is more sensitive to the thin surface layers where as the XRC technique gives an average value over each layer in the heterostructure (if the total thickness is below the penetration depth of the x-ray beam). For ion-damaged epitaxial layers, these two

SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988) / 155

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techniques become complementary in that the rocking curve measures a single total strain caused by both thelattice mismatch and ion -damage, while the Raman shift is from the total strain and ion -damage. In this paper,we use GalnAs layers which were grown by Molecular Beam Epitaxy (MBE) on (001) GaAs substrates. We reportXRC and Raman results on the as -grown layers, on the layers damaged by MeV ion beam, and on the thermalannealing of the ion -damaged layers.

2. EXPERIMENTALS AND RESULTS

GaInAs /GaAs samples were grown by MBE with nominal In contents of 7 %, 12 % and 15 %. For 7% samples,the thicknesses were 100 mn and 1000 nm. For 12 % samples, 5 different thicknesses ranging from 110 nm to250 nm were grown on a 500 nm thick GaAs buffer layer on a semi -insulating GaAs substrate. The latticerelaxation for 100 nm thick sample and the 110 nm sample were undetectable by XRC and. However, the in -planelattice mismatch of the 1000 nm sample was 85 % of the misfit and other samples were relaxed by varyingdegrees. The as -grown sample characteristics are given in Table i. The samples were characterized by XRC forthe film composition, the in -plane lattice constant mismatch, and the elastic strains, and by Raman for the LOphonon frequency. The XRC and topographic measurements of various structural parameters of partially relaxedepilayers are discussed in ref. 12. After the characterization of the as -grown samples, the 7% samples werebombarded at room temperature with 15 MeV Cl ions (range - 5.8 µm in GaAs) and the 12% samples with 9 MeV Pions (range -4.0 µm in GaAs). The particle beam current was typically 10 nA at the particle current density of

100 nA/cm2 for 15 MeV Cl beam and - 2.5 .tA at the particle current density of - 2.5 iA/cm2 for the 9 MeV Pbeam. The beam doses ranged from 5x1011 to 2.5x1015 cm-2. Discussions on the XRC and Raman measurements of2 MeV He bombarded GainAs /GaAs and the 15 MeV Cl bombarded samples are given in ref.6. The ion -bombardedsamples were characterized using XRC and Raman. The two 7 % samples bombarded with 15 MeV Cl ions wereannealed and the strains and LO phonon frequencies were measured as a function of temperature.

2.1 As -grown virgin samples

Before discussing the results on as -grown samples, it is relevant to comment on the critical thickness andlattice relaxation for the samples emloyed in this study. It is by now estabilished that the mechanicalequilibrium theory of Matthews and Blakeslee (M -B) correctly predicts the critical thickness at a given latticemismatch?. However, many experime.ntal data on the critical thickness apparently indicated a much greater

critical thickness than is predicted by the mechanical equilibrium theory13. These observations lead People andBean (P -B) to formulate a model based on the balance of local strain energy density with the energy densityrequired to nucleate a dislocation. The local energy balance mode114 by P -B gave a greater 'critical' thicknessthan that given by M -B and appeared to be in agreement with the experimental data. It was, however, laterproved by Fritz that the disagreement between the equilibrium theory of M -B and the experimental data (mainlyfrom x -ray measurements) is due to the low experimental resolution of the measurement technique and asluggish relaxation of the misfit strain during the initial period13. Measurements on a GaAs/GaInAs /GaAsquantum well structure using much more sensitive techniques such as photoluminescence microscopy and Halleffect measurements indeed gave a critical thickness which is predicted by the M -B theory. The measurementtechnique must be capable of detecting a single dislocation in the whole wafer in order to measure the criticalthickness correctly.

Dodson and coworkers recently presented a phenomenological model based on a relaxation via plastic flow anddislocation multiplication to account for the slow kinetics of strain relaxation15. Dodson also argued that ifsufficient strain energy is provided to nucleate a dislocation locally (as is required as the necessary conditionin the energy balance model by P -B), the level of strain energy is enough to nucleate dislocations everywhere.Therefore, near or above the 'critical' thickness predicted by the local energy balance model of P -B, the lattice

156 / SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988)

techniques become complementary in that the rocking curve measures a single total strain caused by both the lattice mismatch and ion-damage, while the Raman shift is from the total strain and ion-damage. In this paper, we use Gain As layers which were grown by Molecular Beam Epitaxy (MBE) on (001) GaAs substrates. We report XRC and Raman results on the as-grown layers, on the layers damaged by MeV ion beam, and on the thermal annealing of the ion-damaged layers.

2. EXPERIMENTALS AND RESULTS

GalnAs/GaAs samples were grown by MBE with nominal In contents of 7 %, 12 % and 15 %. For 7% samples, the thicknesses were 100 nm and 1000 nm. For 12 % samples, 5 different thicknesses ranging from 110 nm to 250 nm were grown on a 500 nm thick GaAs buffer layer on a semi-insulating GaAs substrate. The lattice relaxation for 100 nm thick sample and the 110 nm sample were undetectable by XRC and. However, the in-plane lattice mismatch of the 1000 nm sample was 85 % of the misfit and other samples were relaxed by varying degrees. The as-grown sample characteristics are given in Table 1. The samples were characterized by XRC for the film composition, the in-plane lattice constant mismatch, and the elastic strains, and by Raman for the LO phonon frequency. The XRC and topographic measurements of various structural parameters of partially relaxed epilayers are discussed in ref. 12. After the characterization of the as-grown samples, the 7% samples were bombarded at room temperature with 15 MeV Cl ions (range ~ 5.8 jim in GaAs) and the 12% samples with 9 MeV P ions (range ~4.0 |J.m in GaAs). The particle beam current was typically 10 nA at the particle current density of ~ 100 nA/cm2 for 15 MeV Cl beam and ~ 2.5 jiA at the particle current density of ~ 2.5 jiA/cm2 for the 9 MeV P beam. The beam doses ranged from 5xl0 11 to 2.5xl015 cm"2 . Discussions on the XRC and Raman measurements of 2 MeV He bombarded GalnAs/GaAs and the 15 MeV Cl bombarded samples are given in ref .6. The ion-bombarded samples were characterized using XRC and Raman. The two 7 % samples bombarded with 15 MeV Cl ions were annealed and the strains and LO phonon frequencies were measured as a function of temperature.

2.1 As-grown virgin samples

Before discussing the results on as-grown samples, it is relevant to comment on the critical thickness and lattice relaxation for the samples emloyed in this study. It is by now established that the mechanical equilibrium theory of Matthews and Blakeslee (M-B) correctly predicts the critical thickness at a given lattice mismatch 7 . However, many experimental data on the critical thickness apparently indicated a much greater critical thickness than is predicted by the mechanical equilibrium theory13 . These observations lead People and Bean (P-B) to formulate a model based on the balance of local strain energy density with the energy density required to nucleate a dislocation. The local energy balance model14 by P-B gave a greater 'critical* thickness than that given by M-B and appeared to be in agreement with the experimental data. It was, however, later proved by Fritz that the disagreement between the equilibrium theory of M-B and the experimental data (mainly from x-ray measurements) is due to the low experimental resolution of the measurement technique and a sluggish relaxation of the misfit strain during the initial period13 . Measurements on a GaAs/GalnAs/GaAs quantum well structure using much more sensitive techniques such as photoluminescence microscopy and Hall effect measurements indeed gave a critical thickness which is predicted by the M-B theory. The measurement technique must be capable of detecting a single dislocation in the whole wafer in order to measure the critical thickness correctly.

Dodson and coworkers recently presented a phenomenological model based on a relaxation via plastic flow and dislocation multiplication to account for the slow kinetics of strain relaxation15 . Dodson also argued that if sufficient strain energy is provided to nucleate a dislocation locally (as is required as the necessary condition in the energy balance model by P-B), the level of strain energy is enough to nucleate dislocations everywhere. Therefore, near or above the 'critical' thickness predicted by the local energy balance model of P-B, the lattice

156 / SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988)

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Table 1 The characteristics of' as -grown samples are given. The x and h arenominal composition in Gai_xInxAs and the nominal thickness. The hc iscalculated critical thickness using the methods of' Matthews and Blakesleeand of People and Bean (in the parenthesis). The x -ray and elastic strainsere discussed in the text. LO is the measured LO phonon frequency inthe GaInAs layer and the Freq. Shift is the strain -induced LO phonon shift.

SampleNo.

x h(nm)

hc(±1m)

E lr

(S)

xr2

(10E3r(56)

Ef

(%)

LO(mil)

ESL

(S)

Freq. Shift(ail)

1 0.07 100 22.5(607) < 0.01 1.16 0.60 291.8 0.55 1.752 0.07 1000 22.5 (607) 0.39 0.61 0.51 289.9 0.10 0.353 0.15 1000 8.5 (99) 0.66 0.87 0.77 288.3 0.10 0.35

509 0.12 110 11.3 (170) <0.01 <0.01 1.41 0.73 292.2 0.67 2.35520 0.12 140 11.3 (170) 0.02 0.02 1.20 0.64 291.9 0.56 1.97

519 0.12 170 11.3 (170) 0.03 0.05 1.19 0.64 291.3 0.55 1.91

508 0.12 200 11.3 (170) 0.07 0.09 1.14 0.63 291.6 0.50 1.76510 0.12 250 11.3 (170) 0.21 0.26 1.17 0.73 290.6 0.44 1.56

0.6

0.5

0.4

0.3

0.2

0.1

1012 10i3 10iß10i5

15 MeV Cl Dose (cm-2 )Fig.i Open circles denote the strains

before bombardment. Samples #2 and #3behave similarly with a bombarded bulk

GaAs (0011. The pseudomorphic sample ( #1)

shows precipitous strain release at a highringp

0.8

0.7

0.6

0.5

0.4

0.3

0.2 t210i3 10" 1015

9 MeV P Dose (cm-2 )Fig.2 Open circles denote strains before

bombardment. The beam -induced strain was

affected by the substantial beam heating(see text) .

a: 509b: 520

- c: 519d: 508e: 510

10"

SPIE Vol 946 Spectroscopic Characterization Techniques for Semiconductor Technology Ill (1988) / 157

Table 1 The characteristics of as-grovn samples are given. The x and h are nominal composition in Gai-xInxAs and the nominal thickness. The hc is calculated critical thickness using the methods of Matthews and Blakeslee and of People and Bean (in the parenthesis). The x-ray and elastic strains are discussed in the text. LO is the measured LO phonon frequency in the Gain As layer and the Freq. Shift is the strain-induced LO phonon shift.

Sample x No.

1

23509520519

508

510

0.070.070.15

0.120.120.12

0.120.12

h (am)

10010001000

110140

170

200

250

22.22

8

1111.

11.

11.

11.

(am)

5(607)5(607).5(99)

3(170)3(170)3(170)3(170)3(170)

<«

< 0.010.390.66

<0.010.02

0.03

0.07

0.21

(%)

.

<0.010.02

0.05

0.09

0.26

(*>

1.160.610.87

1.411.20

1.19

1.14

1.17

(*)

0.600.510.77

0.730.64

0.64

0.63

0.73

LO (cm 1)

291.8289.9288.3

292.2291.9

291.3291.6

290.6

<?>0.550.100.10

0.670.56

0.550.500.44

Freq. Shift (cm 1)

1.750.350.35

2.351.9?1.91

1.761.56

0.6

0.5

£ 0.4

CD

4Jcn

OT

S 0.2LU

0.1

10 11 10 12 10 13 10 14 10 1610 15

15 MeV Cl Dose (cm'2 ) Fig.l Open circles denote the strains before bombardment. Samples #2 and #3 behave similarly with a bombarded bulk GaAs(OOi). The pseudomorphic sample (#1) shows precipitous strain release at a high dose.

O.B

0.7

* 0.6

toL. -P C/J 0.5

(05 0.4QJ

0.3

0.210 12

1010 13 10 14 10 15

9 MeV P Dose (cm'2 )Fig.2 Open circles denote strains before bombardment. The beam-induced strain was affected by the substantial beam heating (see text) .

16

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relaxation is sufficiently high that the relaxation can be easily measured by the x -ray rocking curve technique.At a given lattice mismatch (or composition) the epitaxial layer is usually near the perfectly coherent state at alayer thickness above the critical thickness given by M -B, provided that it is well below the 'critical' given byP -B. This is due to the sluggish relaxation of strain.

We list in Table 1 the critical thicknesses, hc, calculated by the mechanical equilibrium theory of M -B and

by the local energy balance model of P -B (which is given in the parenthesis) are listed in Table 1 using thenominal composition for the film. The x -ray strains E 1xr, E2xr, and E3xr are given in Table 1. The x -ray strains

give the film lattice spacings relative to the substrate for three directions, that is, Eixr = (di- ds) /ds where

dland d2 are film lattice spacings along the two <110> directions in the sample plane, d3 is the film lattice

spacing along surface normal, and ds is the substrate lattice spacings along corresponding directions. It is

noticed that, within the minimum in -plane mismatch which is detectable by the XRC technique (which is about0.01% in lattice constant mismatch in the sample plane), no lattice relaxation is observed for the 1100 A -thick#509 (equilibrium critical thickness by M -B= 140 A) and for the 1000 A -thick #1 (critical thickness =225 A).For thicker films in the 500 series the relaxation is observed. The in -plane mismatch is about 0.02% for 1400 A( #520), 0.03 -0.05% for 1700 A ( #519), 0.07 -0.09% for 2000 A ( #508), and 0.21 -0.26% for 2500A ( #510).Notice that at 2500 A, more than 30% of the initial misfit strain is relaxed. For #519 and #520, the strainrelaxation is quite small, being less than 6% of the original misfit strain. For partially relaxed samples, thelattice relaxations along the two <110> directions are different from each other12. This is indicated by thedifferent values of the two parallel x -ray strains for #519, #508, and #510 in Table 1 (The parallel strains alongthe other <110> direction for #2 and #3 were not measured.) The difference in relaxation along the two <110>direction, i.e., E1xr - E2xr, produces an additional unit cell distortion (i.e., in addition to the already existing

tetragonal distortion). The XRC measurement of the layer composition, the in -plane lattice parameter mismatch(parallel x -ray strain), the elastic strain, and the average spacing of misfit dislocations for partiallylattice -relaxed epilayers are discussed in detail in ref. 12.

The misfit, Ef = (aras)/as where of and as are the bulk lattice constants for the film and the substrate,

respectively, are obtained from the XRC data and are given in Table 1. These values of misfit correspond to anindium content x in the film of 0.084 for #1, 0.07 for #2, 0.11 for #3, 0.102 for #509 and #510, and 0.089 for#520, #519, and #508. These values are slightly different from the nominal composition values. This ispartially due to the fact that an elasticity theory is used to calculate the composition from the XRC data, notconsidering the plastic deformation from the relaxation process. The LO phonon frequencies and thestrain- induced frequency shifts for the GalnAs epilayers have been discussed in ref. 1 for the samples #1, #2and #3. Briefly, the strain- induced phonon -shift was calculated using the XRC data on elastic strain and thephonon deformation constant9 and was substracted from the measured LO phonon frequency. Resultingbulk -equivalent LO phonon frequencies were plotted as a function of the In content "x" in Ga1_xlnxAst. The

frequency shifts listed in Table 1 are the strain- induced shifts.

2.2 MeV -ion damaged GalnAs /GaAs

The MeV ions stop at 3 -5 µm below the GalnAs layer. The nuclear stopping power, i.e., the energy loss perunit length into an atomic displacement process, in the Gao 9Ino 1As layer is about 2.77 eV /A for the 15 MeV Cl

ion and 2.93 eV /A for the 9 MeV P ion at the incident ion energy, as calculated from the Kr-C formula in ref. 16.

So, we can assume a similar amount of ion -damage for both ions at the same dose. Also, the nuclear stopping

power for these MeV ions varies very slowly with depth in the near- surface layer4 so that we can assume an

approximately uniform damage level in the 0.1 -1µm thick GalnAs layer.

158 / SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology Ill (1988)

relaxation is sufficiently high that the relaxation can be easily measured by the x-ray rocking curve technique. At a given lattice mismatch (or composition) the epitaxial layer is usually near the perfectly coherent state at a layer thickness above the critical thickness given by M-B, provided that it is well below the 'critical1 given by P-B. This is due to the sluggish relaxation of strain.

We list in Table 1 the critical thicknesses, hc, calculated by the mechanical equilibrium theory of M-B and

by the local energy balance model of P-B (which is given in the parenthesis) are listed in Table 1 using the nominal composition for the film. The x-ray strains e^**, £<£*, and e^** &* given in Table 1. The x-ray strains

give the film lattice spacings relative to the substrate for three directions, that is, e™ = (d^-ds)/ds where

djand ^ are ^m lattice spacings along the two <110> directions in the sample plane, d^ is the film lattice

spacing along surface normal, and dg is the substrate lattice spacings along corresponding directions. It is

noticed that, within the minimum in-plane mismatch which is detectable by the XRC technique (which is about 0.01% in lattice constant mismatch in the sample plane), no lattice relaxation is observed for the 1100 A-thick#509 (equilibrium critical thickness by M-B= 140 A) and for the 1000 A-thick #1 (critical thickness=225 A). For thicker films in the 500 series the relaxation is observed. The in-plane mismatch is about 0.02% for 1400 A (#520), 0.03-0.05% for 1700 A (#519), 0.07-0.09% for 2000 A (#508), and 0.21-0.26% for 2500A (#510). Notice that at 2500 A, more than 30% of the initial misfit strain is relaxed. For #519 and #520, the strain relaxation is quite small, being less than 6% of the original misfit strain. For partially relaxed samples, the lattice relaxations along the two <110> directions are different from each other 12 . This is indicated by the different values of the two parallel x-ray strains for #519, #508, and #510 in Table 1 (The parallel strains along the other <110> direction for #2 and #3 were not measured.) The difference in relaxation along the two <110> direction, i.e., e^ - 62Xr, produces an additional unit cell distortion (i.e., in addition to the already existing

tetragonal distortion). The XRC measurement of the layer composition, the in-plane lattice parameter mismatch (parallel x-ray strain), the elastic strain, and the average spacing of misfit dislocations for partially lattice-relaxed epilayers are discussed in detail in ref. 12.

The misfit, 6f = (af-ag)/as where a^ and as are the bulk lattice constants for the film and the substrate,

respectively, are obtained from the XRC data and are given in Table 1. These values of misfit correspond to an indium content x in the film of 0.084 for #1,0.07 for #2, 0.11 for #3,0.102 for #509 and #510, and 0.089 for#520, #519, and #508. These values are slightly different from the nominal composition values. This is partially due to the fact that an elasticity theory is used to calculate the composition from the XRC data, not considering the plastic deformation from the relaxation process. The LO phonon frequencies and the strain-induced frequency shifts for the GalnAs epilayers have been discussed in ref. 1 for the samples #1, #2 and #3. Briefly, the strain-induced phonon-shift was calculated using the XRC data on elastic strain and the phonon deformation constant9 and was substracted from the measured LO phonon frequency. Resulting bulk-equivalent LO phonon frequencies were plotted as a function of the In content "x" in Ga^_xInxAs 1 . The

frequency shifts listed in Table 1 are the strain-induced shifts.

2.2 MeV-ion damaged GalnAs/GaAs

The MeV ions stop at 3 - 5 urn below the GalnAs layer. The nuclear stopping power, i.e., the energy loss per unit length into an atomic displacement process, in the GaQ ^InQ j As layer is about 2.77 eV/A for the 15 MeV Cl

ion and 2.93 eV/A for the 9 MeV P ion at the incident ion energy, as calculated from the Kr-C formula in ref. 16. So, we can assume a similar amount of ion-damage for both ions at the same dose. Also, the nuclear stopping power for these MeV ions varies very slowly with depth in the near-surface layer4 so that we can assume an approximately uniform damage level in the 0.1 -1 urn thick GalnAs layer.

158 / SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988)

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293

292

Vie 29i

>. 290uC0Q 289NL

LL288

oC.c 287ao-I 286

285

2810ísí0s2 10ía 10" 10i5 10l6

15 MeV Cl Dose (cm"2 )

Fig.3 Circled points are the data before

bombardment. The beam -induced shift at

maximum dose is about -2 in the

pseudomorphic sample (#1) and about -4 in

the relaxed samples ( #2 and #3).

0.6

0.5

0.4

C.rel

f0L

0.3

u.m4.)

tN

° 0.2W

0.1

00 100 200 300 400 500 600

Annealing Temperature ( °C)

Fig.5 Samples bombarded to a high dose

with 15 MeV Cl. Circle- unbombarded;

square -as- bombarded; triangle -i.5 year

aged at 30 -35 C; p -in -plane mismatch for

#2.

293

292

É 291u

290uCNQ 289NL

288oCi 287a_

e-' 286

285

2841012 1013

10" 10"9 MeV P Dose (cm 2 )

Fig.4 Circles denote pre- bombardment

values. Drawn to the same scale with Fig.3

for comparison. Beam -induced shifts at

maximum dose range from -0.4 to -1.3. This

small shift is due to beam heating (300C) .

a: 509- b: 520c: 519

- d: 508. e: 510

294

293

292..Eu` 29iu

290o'

ii 289Cog 288

ó 287

286

2850 100 200 300 400 500 600

Annealing Temperature ( °C)

Fig.6 Symbols have the same meaning as in

Fig.5. Samples are bombarded with 15 MeVCl to a high dose. Data for as-grown

samples are marked by the dashed (#1) anddotted (#2) lines.

SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology 111(1988) / 159

u03

0)

oc o

293

292

291

290

289

288

287

286

285

284

293

292

291

290

OJ

or0)

&.oc

10 1 1010 12 10 13 10" 10 15 15 MeV Cl Dose (cm"2 )

Fig.3 Circled points are the data before bombardment. The beam-induced shift at maximum dose is about -2 in the pseudomorphic sample (til and about -4 in the relaxed samples (#2 and #3) .

16

289

288

287

286

285

284

a: 509 b: 520 c: 519 d: 508 e: 510

10 X 10 12 10 1810 13 10" 10 15 9 MeV P Dose (cm"2 )

Fig.4 Circles denote pre-bombardment values. Drawn to the same scale with Fig.3 for comparison. Beam-induced shifts at maximum dose range from -0.4 to -1.3. This small shift is due to beam heating (300 0 .

0.6

0.5

S 0.4

10

-*-1 en

(0

5 0.2

0.1

0 100 200 300 400 500 600Annealing Temperature (°C)

Fig.5 Samples bombarded to a high dose with 15 MeV Cl. Circle-unbombarded; square»as-bombarded; triangle=1.5 year aged at 30-35 C; p«in-plane mismatch for

294

293

JT 292

u~ 291u§ 290or0)

it 289

oi 288

q 287

286

2856000 100 200 300 400 500

Annealing Temperature (°C) Fig.6 Symbols have the same meaning as in Fig.5. Samples are bombarded with 15 MeV Cl to a high dose. Data for as-grown samples are marked by the dashed (#1) and dotted (#2) lines.

SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988) / 159

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Figure 1 shows the elastic strain in the GalnAs epitaxial layer (the component along the surface normal) as afunction of beam dose for the 15 MeV Cl ion bombarded samples. These are samples named 1, 2, and 3 in Table 1and the symbols in the figure all correspondingly 1, 2, and 3. Data points in an open circle designate valuesbefore irradiation. For the 1 gm thick samples #2 and #3 (both are well above the 'critical' thickness of theenergy balance model), the elastic strain varies from 0.1 % at zero dose to 0.25 - 0.3% at the maximum dose.Theus, beam -induced increase of the elastic strain, 0.15 - 0.2 %, in these very- relaxed GalnAs epilayers is veryclose to the beam -induced elastic strain, - 1.9 %, in the bulk GaAs(001) samples bombarded with the same ions4.This observation is also consistent with the LO phonon frequency shift data in these two samples (see Figure 3).The elastic strains in the ion - bombarded pseudomorphic samples, #1 and #509, behave quite differently. Forthe 15 MeV Cl ion - bombarded sample #1 (see Figure 1) and the 9 MeV P ion - bombarded #509 (see Figure 2), theelastic strain drops at the lowest beam dose and then increases with beam dose. At the high dose region (at2.5x1014 for Cl and at 5x1015 cm-2 for P), there occurs another drop in the elastic strain. This drop at the highdose seems to correspond to a similar phenomenon observed in an ion -implanted strained layer superlattice(SLS) GalnAs /GaAs samples by Myers and coworkers17. In the 15 MeV Cl ion -bombarded single GainAs layer, the

precipitous strain release seems to occur at a damage energy density of about 3x1019 keV /cm3 (The correspondingenergy deposition was about an order of magnitude higher presumably because of the beam- induced heating).However, the pseudomorphic samples remained pseudomorphic at all doses (i.e., E1xr < 0.01 % at all doses).

The 250 nm thick #510, which had the largest initial relaxation (see Table 1) compared with the otherpartially relaxed samples ( #520, #519, and #508), further relaxes substantially in the beam -bombardedsamples as seen in Figure 2. The drop of elastic strain in the bombarded layers for #510 is accompanied by anincrease in the in -plane mismatch (i.e., E1xr in Table 1) from 0.24 ± 0.03 % in the unbombarded sample to 0.45 ±0.04 % in the bombarded layers. The in -plane mismatch (or lattice relaxation) after 9 MeV P ion bombardmentfor other partially relaxed samples varies over 0 - 0.03 % for 140 nm thick #520, 0.02 - 0.06 % for 170 nm thick#519, 0.04 - 0.11 % for 200 nm thick #508. The degree of lattice relaxation in these partially relaxed samplesvaried irregularly for different samples at different doses within the above -given ranges (as the elastic strainsvary irregularly with beam dose in Figure 2). The degree of lattice relaxation also seemed quite nonuniformwithin each sample, as -grown or ion -bombarded.

The LO phonon frequencies are shown as a function of beam doses in Figure 3 and Figure 4. The data points inan open circle correspond to data before bombardment. At the maximum dose, the beam -induced phonon shifts(4 -5 cm-1) in the very -relaxed #2 and #3 are similar to the beam- induced shift in bulk GaAs bombarded to thesame doses. However, in the relatively thin (0.1 - 0.25 µm) samples the beam- induced shifts of 0.5 - 2.5 cm-1 atthe maximum dose are much samller than in the 1 gm thick samples. However, the 9 MeV P ion implantedsamples showed a sign of a substantial beam heating effect. The beam- induced temperature rise in the GaInAslayer during the ion irradiation was estimated by the following way. The normal x -ray strain along the surfacenormal in a bulk GaAs(001) wafer was shown to saturate at - 0.4% at high beam doses when bombarded with a lowcurrent (- 10 nA) MeV ion beam (independent of ion species)4. However, the normal x -ray strain in theGaAs(001) substrates of the 9 MeV P ion implanted GaInAs/GaAs samples was about 0.13% at the maximum dose.This value corresponds to a GaAs(001) sample which was bombarded to the saturation of strain and subsequentlyannealed to about 300 °C18. The Raman shifts in the P ion bombarded films also are close to the shifts we obtainfrom the Cl ion bombarded and subsequently annealed samples discussed in next section (see Fig.6). Therefore,we believe that the high beam current (2.5 RA) of the 9 MeV P ions raises the target temperature close to 300 °C.

2.3 Thermal annealing behavior of the ion -damaged GaInAs layers

Conventional furnace annealing was performed on the samples #1 and #2 bombarded to a high dose at

160 / SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology Ill (1988)

Figure 1 shows the elastic strain in the GalnAs epitaxial layer (the component along the surface normal) as a function of beam dose for the 15 MeV Cl ion bombarded samples. These are samples named 1,2, and 3 in Table 1 and the symbols in the figure all correspondingly 1,2, and 3. Data points in an open circle designate values before irradiation. For the 1 ^im thick samples #2 and #3 (both are well above the 'critical1 thickness of the energy balance model), the elastic strain varies from 0.1 % at zero dose to 0.25 - 0.3% at the maximum dose. Theus, beam-induced increase of the elastic strain, 0.15 - 0.2 %, in these very-relaxed GalnAs epilayers is very close to the beam-induced elastic strain, ~ 1.9%, in the bulk GaAs(OOl) samples bombarded with the same ions4 . This observation is also consistent with the LO phonon frequency shift data in these two samples (see Figure 3). The elastic strains in the ion-bombarded pseudomorphic samples, #1 and #509, behave quite differently. For the 15 MeV Cl ion-bombarded sample #1 (see Figure 1) and the 9 MeV P ion-bombarded #509 (see Figure 2), the elastic strain drops at the lowest beam dose and then increases with beam dose. At the high dose region (at 2.5xl014 for Cl and at 5xl015 cm"2 for P), there occurs another drop in the elastic strain. This drop at the high dose seems to correspond to a similar phenomenon observed in an ion-implanted strained layer superlattice (SLS) GalnAs/GaAs samples by Myers and coworkers 17 . In the 15 MeV Cl ion-bombarded single GalnAs layer, the precipitous strain release seems to occur at a damage energy density of about 3xl019 keV/cm3 (The corresponding energy deposition was about an order of magnitude higher presumably because of the beam-induced heating). However, the pseudomorphic samples remained pseudomorphic at all doses (i.e., e™ < 0.01% at all doses).

The 250 nm thick #510, which had the largest initial relaxation (see Table 1) compared with the other partially relaxed samples (#520, #519, and #508), further relaxes substantially in the beam-bombarded samples as seen in Figure 2. The drop of elastic strain in the bombarded layers for #510 is accompanied by an increase in the in-plane mismatch (i.e., e™ in Table 1) from 0.24 ± 0.03 % in the unbombarded sample to 0.45 ± 0.04 % in the bombarded layers. The in-plane mismatch (or lattice relaxation) after 9 MeV P ion bombardment for other partially relaxed samples varies over 0 - 0.03 % for 140 nm thick #520, 0.02 - 0.06 % for 170 nm thick #519,0.04 - 0.11 % for 200 nm thick #508. The degree of lattice relaxation in these partially relaxed samples varied irregularly for different samples at different doses within the above-given ranges (as the elastic strains vary irregularly with beam dose in Figure 2). The degree of lattice relaxation also seemed quite nonuniform within each sample, as-grown or ion-bombarded.

The LO phonon frequencies are shown as a function of beam doses in Figure 3 and Figure 4. The data points in an open circle correspond to data before bombardment. At the maximum dose, the beam-induced phonon shifts (4-5 cm) in the very-relaxed #2 and #3 are similar to the beam-induced shift in bulk GaAs bombarded to the same dose5 . However, in the relatively thin (0.1 - 0.25 |4,m) samples the beam-induced shifts of 0.5 - 2.5 cnf * at the maximum dose are much samller than in the 1 |im thick samples. However, the 9 MeV P ion implanted samples showed a sign of a substantial beam heating effect. The beam-induced temperature rise in the GalnAs layer during the ion irradiation was estimated by the following way. The normal x-ray strain along the surface normal in a bulk GaAs(OOl) wafer was shown to saturate at ~ 0.4% at high beam doses when bombarded with a low current (~ 10 nA) MeV ion beam (independent of ion species)4 . However, the normal x-ray strain in the GaAs(OOl) substrates of the 9 MeV P ion implanted GalnAs/GaAs samples was about 0.13% at the maximum dose. This value corresponds to a GaAs(OOl) sample which was bombarded to the saturation of strain and subsequently annealed to about 300 °C 18 . The Raman shifts in the P ion bombarded films also are close to the shifts we obtain from the Cl ion bombarded and subsequently annealed samples discussed in next section (see Fig.6). Therefore, we believe that the high beam current (2.5 }jA) of the 9 MeV P ions raises the target temperature close to 300 °C.

2.3 Thermal annealing behavior of the ion-damaged GalnAs layers

Conventional furnace annealing was performed on the samples #1 and #2 bombarded to a high dose at

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temperatures up to 500 °C because the damage in the near -surface region is completely annealed out at 500 °C inthe MeV heavy ion bombarded bulk GaAs crystals18. The samples #1 and #2 bombarded to 1.25x1015 cm-2 with 15

MeV Cl ions were used to study the strain recovery, and same samples bombarded to 2.5x1015 cm-2 were used tostudy the recovery of Raman frequency. Annealing was done for 15 minutes with a proximity cap using a GaAswafer to suppress to arsenic out -diffusion under a small flow of forming gas. However, no provisions were takenfor the possible indium decomposition from the surface of GaInAs.

Figure 5 shows the thermal annealing behavior of elastic strains for #1 and #2 and the anneal behavior of theparallel x -ray strain (i.e., in -plane mismatch) for sample #2. All of these samples were bombarded with asaturation dose of 15 MeV Cl ions. The data points in an open square are for the as- bombarded samples and thosein an open triangle are for the samples aged at room temperature (30 - 35 °C) for about 1.5 years. The parallelx -ray strain for sample #1 was less than 0.01 % (minimum in -plane mismatch that can be detected by XRC) at alltemperatures. That is, it remained pseudomorphic within the XRC resolution. The parallel x -ray strain forsample #2 also did not change with annealing temperature, being kept constant at about 0.31% (see Figure 5).Therefore, it can be said that the lattice relaxation of GaInAs/GaAs does not change by annealing up to 500 °C(which is less than the epitaxial growth temperature in MBE). However, the elastic strain for #1 in the directionnormal to the surface decreases monotonically with temperature to a value which is significantly smaller thanthe pre -bombardment value. Remember that all the radiation damage is expected to be fully recovered by 500 °C.Since there is no change in the lattice constants in the sample plane, a similar decrease will occur in thebulk -equivalent cubic cell lattice constant for the epilayer. This indicates loss of indium from the 100 nm thickepilayer due to thermal annealing. The indium content for #1 at 500 °C estimated from the XRC data is about0.05 - 0.06 (pre- bombardment In content by XRC = 0.08). The normal elastic strain for sample #2, however,recovers back to the pre -bombardment value at 500 °C. The indium -loss is not obvious in the XRC data for #2presumably because indium is lost primarily from the surface -100 nm layer with little change in the remaining-900 nm. These XRC data combined with the Raman data (discussed below) indicate that the indium is lostpredominantly from the surface - 100 nm layer while it does not show any observable change in deeper regions.

Figure 6 shows the LO phonon frequencies for samples #1 and #2 as a function of annealing temperature.Also shown in the figure are, in open circles, the Raman frequencies from unbombarded virgin layers of #1 and#2 at room temperature, at 407 °C and at 508 °C. The Raman frequencies at 300 -500 °C of the bombarded orunbombarded layers are higher than in the as -grown layer. This increase implies also loss of indium in thesurface 100 nm layer, consistent with the XRC data. Assuming that all the ion -damage was recovered by 500 °C,if we substract the strain- induced Raman shift from the measured values for sample #1 annealed at 500 °C, the

bulk -equivalent frequency is higher by 1.3 - 1.8 cm-1 in the annealed sample than in an as-grown sample. This

bulk -equivalent Raman frequency (291.1 - 291.6 cm-1 ) in #1 annealed at 500 °C corresponds to an indiumcontent of 0.03 - 0.05 in the LO phonon versus x data in ref. 1. This result is consistent with the compositionfrom the XRC data within an experimental error.

In summary, both the x -ray and the Raman data indicate a substantial loss of indium from the surface 100 nmthick layer due to annealing up to 500 °C. The XRC data show that the lattice relaxation is unchanged byannealing up to 500 °C.

3. ACKNOWLEDGMENT

The SUNY- Buffalo portion of this work was supported in part by the Office of Naval Research under thecontract number N00014 -87 -K -0799.

SP /E Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology 111 (1988) 1 161

temperatures up to 500 °C because the damage in the near-surface region is completely annealed out at 500 °C in the MeV heavy ion bombarded bulk GaAs crystals 18 . The samples #1 and #2 bombarded to 1.25xl015 cm"2 with 15 MeV Cl ions were used to study the strain recovery, and same samples bombarded to 2.5xl015 cm"2 were used to study the recovery of Raman frequency. Annealing was done for 15 minutes with a proximity cap using a GaAs wafer to suppress to arsenic out-diffusion under a small flow of forming gas. However, no provisions were taken for the possible indium decomposition from the surface of GalnAs.

Figure 5 shows the thermal annealing behavior of elastic strains for #1 and #2 and the anneal behavior of the parallel x-ray strain (i.e., in-plane mismatch) for sample #2. All of these samples were bombarded with a saturation dose of 15 MeV Cl ions. The data points in an open square are for the as-bombarded samples and those in an open triangle are for the samples aged at room temperature (30 ~ 35 °C) for about 1.5 years. The parallel x-ray strain for sample #1 was less than 0.01 % (minimum in-plane mismatch that can be detected by XRC) at all temperatures. That is, it remained pseudomorphic within the XRC resolution. The parallel x-ray strain for sample #2 also did not change with annealing temperature, being kept constant at about 0.31% (see Figure 5). Therefore, it can be said that the lattice relaxation of GalnAs/GaAs does not change by annealing up to 500 °C (which is less than the epitaxial growth temperature in MBE). However, the elastic strain for #1 in the direction normal to the surface decreases monotonically with temperature to a value which is significantly smaller than the pre-bombardment value. Remember that all the radiation damage is expected to be fully recovered by 500 °C. Since there is no change in the lattice constants in the sample plane, a similar decrease will occur in the bulk-equivalent cubic cell lattice constant for the epilayer. This indicates loss of indium from the 100 nm thick epilayer due to thermal annealing. The indium content for #1 at 500 °C estimated from the XRC data is about 0.05 - 0.06 (pre-bombardment In content by XRC = 0.08). The normal elastic strain for sample #2, however, recovers back to the pre-bombardment value at 500 °C. The indium-loss is not obvious in the XRC data for #2 presumably because indium is lost primarily from the surface ~100 nm layer with little change in the remaining ~900 nm. These XRC data combined with the Raman data (discussed below) indicate that the indium is lost predominantly from the surface ~ 100 nm layer while it does not show any observable change in deeper regions.

Figure 6 shows the LO phonon frequencies for samples #1 and #2 as a function of annealing temperature. Also shown in the figure are, in open circles, the Raman frequencies from unbombarded virgin layers of #1 and #2 at room temperature, at 407 °C and at 508 °C. The Raman frequencies at 300-500 °C of the bombarded or unbombarded layers are higher than in the as-grown layer. This increase implies also loss of indium in the surface 100 nm layer, consistent with the XRC data. Assuming that all the ion-damage was recovered by 500 °C, if we substract the strain-induced Raman shift from the measured values for sample #1 annealed at 500 °C, the bulk-equivalent frequency is higher by 1.3 -1.8 cm" 1 in the annealed sample than in an as-grown sample. This bulk-equivalent Raman frequency (291.1 - 291.6 cm" 1 ) in #1 annealed at 500 °C corresponds to an indium content of 0.03 - 0.05 in the LO phonon versus x data in ref. 1. This result is consistent with the composition from the XRC data within an experimental error.

In summary, both the x-ray and the Raman data indicate a substantial loss of indium from the surface 100 nm thick layer due to annealing up to 500 °C. The XRC data show that the lattice relaxation is unchanged by annealing up to 500 °C.

3. ACKNOWLEDGMENT

The SUNY-Buffalo portion of this work was supported in part by the Office of Naval Research under the contract number N00014-87-K-0799.

SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988) / 161

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4_REFERENCES

1. G. Burns, C.R. Wie, F.H. Dacol, G.D. Pettit, and J.M. Woodall, "Phonon shifts and strains in strain- layered(Ga1_xInx)As," Appl. Phys. Lett. 51(23), 1919 -1921 (1987).

2. M. Nakayama, K. Kubota, T. Kanata, H. Kato, S. Chika, and N. Sano, "Raman study of GaAs- InxAli_xAs

strained -layer superlattices," J. Appl. Phys. 58(11), 4342 -4345 (1985),V.S. Speriosu and T. Vreeland, Jr., "X -ray rocking curve analysis of superlattices," J. Appl. Phys. 56(6),1591 -1600 (1984).

3. K.K. Tiong, P.M. Amirtharaj, F.H. Pollak, and D.E. Aspnes, "Effects of As ion implantation on the Ramanspectra of GaAs: 'Spatial correlation' interpretation," Appl. Phys. Lett. 44(1), 122 -124 (1984).

4. C.R. Wie, T.A. Tombrello and T. Vreeland, Jr., "MeV ion damage in GaAs single crystals: Strain saturation androle of nuclear and electronic collisions in defect production," Phys. Rev. B 33(6), 4083 -4089 (1986).

5. G. Burns, F.H. Dacol, C.R. Wie, E. Burstein, and M. Cardona, "Phonon shifts in ion bombarded GaAs: Ramanmeasurements," Solid State Commun. 62(7), 449 -454 (1987).

6. C.R. Wie, K. Xie, G. Bums, F.H. Dacol, G.D. Pettit, and J.M. Woodall, "X -ray and Raman studies of MeV ionimplanted GalnAs/GaAs," Matr. Res. Soc. Symp. Proc. E104 (1988), in press.

7. J.W. Matthews and A.E. Blakeslee, "Defects in epitaxial multilayers," J. Cryst. Growth 27, 118 -125 (1974)8. C.R. Wie, T.A. Tombrello and T. Vreeland, Jr., "Dynamical x -ray diffraction from nonuniform crystalline

films: Application to x -ray rocking curve analysis," J. Appl. Phys. 59(11), 3743 -3746 (1986).9. F. Cerdeira, C.J. Buchenauer, F.H. Pollak, and M. Cardona, "Stress- induced shifts of first -order Raman

frequencies of diamond - and zincblende -type semiconductors, " Phys. Rev. B 5(2), 580 -593 (1972).10.D.J. Olego, H. Baumgart and G.K. Celler, "Strains in Si- on -SiO2 structures formed by oxygen implantation:

Raman scattering characterization," Appl. Phys. Lett. 52(6), 483 -485 (1988).11. H. Shen and F.H. Pollak, "Raman study of polish- induced surface strain in <100> GaAs and InP," Appl. Phys.

Lett. 45(6), 692 -694 (1984).12. C.R. Wie, H.M. Kim and K.M. Lau, "Nondestructive characterization of MOCVD -grown GaInAs/GaAs using

rocking curve and topography," in Proc. SPIE Vol. 877 (1988), in press.13. I.J. Fritz, "Role of experimental resolution in measurements of critical layer thickness for strained -layer

epitaxy," Appl. Phys. Lett. 51(14), 1080 -1082 (1987).14. R. People and J.C. Bean, "Calculation of critical layer thickness versus lattice mismatch for GexSil /Si

strained -layer heterostructures," Appl. Phys. Lett. 47(3), 322 -324 (1985).15. B.W. Dodson and J.Y. Tsao, "Relaxation of strained -layer semiconductor structures via plastic flow," Appl.

Phys. Lett. 51(17), 1325 -1327 (1987).16. W.D. Wilson, L.G. Haggmark and J.P. Biersack, "Calculation of nuclear stopping, ranges, and straggling in the

low- energy region," Phys. Rev. B 15(5), 2458 -2468 (1977).17. D.R. Myers, G.W. Arnold, C.R. Hills, L.R. Dawson, and B.L. Doyle, "High -fluence ion damage effects in

Ar- implanted (InGa)As /GaAs strained -layer superlattices," Appl. Phys. Lett. 51(11), 820 -822 (1987).18. C.R. Wie, T. Vreeland, Jr., and T.A. Tombrello, "MeV ion -damage in Ill -V semiconductors: saturation and

thermal annealing of strain in GaAs and GaP crystals," Nucl. Instr. Meth. B16, 44 -49 (1986).

162 / SPIE Vol 946 Spectroscopic Characterization Techniques for Semiconductor Technology Ill (1988)

4. REFERENCES

1. G. Burns, C.R. Wie, F.H. Dacol, G.D. Pettit, and J.M. Woodall, "Phonon shifts and strains in strain-layered (Ga^In^As," Appl. Phys. Lett. 51(23), 1919-1921 (1987).

2. M. Nakayama, K. Kubota, T. Kanata, H. Kato, S. Chika, and N. Sano, "Raman study of GaAs-InxAl 1-xAs

strained-layer superlattices," J. Appl. Phys. 58(11), 4342-4345 (1985),V.S. Speriosu and T. Vreeland, Jr., "X-ray rocking curve analysis of superlattices," J. Appl. Phys. 56(6), 1591-1600(1984).

3. K.K. Tiong, P.M. Amirtharaj, F.H. Pollak, and D.E. Aspnes, "Effects of As+ ion implantation on the Raman spectra of GaAs: 'Spatial correlation1 interpretation," Appl. Phys. Lett. 44(1), 122-124 (1984).

4. C.R. Wie, T.A. Tombrello and T. Vreeland, Jr., "MeV ion damage in GaAs single crystals: Strain saturation and role of nuclear and electronic collisions in defect production," Phys. Rev. B 33(6), 4083-4089 (1986).

5. G. Burns, F.H. Dacol, C.R. Wie, E. Burstein, and M. Cardona, "Phonon shifts in ion bombarded GaAs: Raman measurements," Solid State Commun. 62(7), 449-454 (1987).

6. C.R. Wie, K. Xie, G. Burns, F.H. Dacol, G.D. Pettit, and J.M. Woodall, "X-ray and Raman studies of MeV ion implanted GalnAs/GaAs," Matr. Res. Soc. Symp. Proc. E104 (1988), in press.

7. J.W. Matthews and A.E. Blakeslee, "Defects in epitaxial multilayers," J. Cryst. Growth 27, 118-125 (1974)8. C.R. Wie, T.A. Tombrello and T. Vreeland, Jr., "Dynamical x-ray diffraction from nonuniform crystalline

films: Application to x-ray rocking curve analysis," J. Appl. Phys. 59(11), 3743-3746 (1986).9. F. Cerdeira, CJ. Buchenauer, F.H. Pollak, and M. Cardona, "Stress-induced shifts of first-order Raman

frequencies of diamond- and zincblende-type semiconductors," Phys. Rev. B 5(2), 580-593 (1972).10.D.J. Olego, H. Baumgart and O.K. Celler, "Strains in Si-on-SiC>2 structures formed by oxygen implantation:

Raman scattering characterization," Appl. Phys. Lett. 52(6), 483-485 (1988).11. H. Shen and F.H. Pollak, "Raman study of polish-induced surface strain in <100> GaAs and InP," Appl. Phys.

Lett. 45(6), 692-694 (1984).12. C.R. Wie, H.M. Kim and K.M. Lau, "Nondestructive characterization of MOCVD-grown GalnAs/GaAs using

rocking curve and topography," in Proc. SPffi Vol. 877 (1988), in press. 13.1.J. Fritz, "Role of experimental resolution in measurements of critical layer thickness for strained-layer

epitaxy," Appl. Phys. Lett. 51(14), 1080-1082 (1987).14. R. People and J.C. Bean, "Calculation of critical layer thickness versus lattice mismatch for GexSij_x/Si

strained-layer heterostructures," Appl. Phys. Lett. 47(3), 322-324 (1985).15. B.W. Dodson and J.Y. Tsao, "Relaxation of strained-layer semiconductor structures via plastic flow," Appl.

Phys. Lett. 51(17), 1325-1327 (1987).16. W.D. Wilson, L.G. Haggmark and J.P. Biersack, "Calculation of nuclear stopping, ranges, and straggling in the

low-energy region," Phys. Rev. B 15(5), 2458-2468 (1977).17. D.R. Myers, G.W. Arnold, C.R. Hills, L.R. Dawson, and B.L. Doyle, "High-fluence ion damage effects in

Ar-implanted (InGa)As/GaAs strained-layer superlattices," Appl. Phys. Lett. 51(11), 820-822 (1987).18. C.R. Wie, T. Vreeland, Jr., and T.A. Tombrello, "MeV ion-damage in in-V semiconductors: saturation and

thermal annealing of strain in GaAs and GaP crystals," Nucl. Instr. Meth. B16,44-49 (1986).

162 / SPIE Vol. 946 Spectroscopic Characterization Techniques for Semiconductor Technology III (1988)

Downloaded From: http://proceedings.spiedigitallibrary.org/ on 09/07/2013 Terms of Use: http://spiedl.org/terms