SixGe1-x and SixGe1-xOy Films as a Thermal Sensing Material

Mukti Rana and Donald Butler

University of Texas at Arlington

Electrical Engineering Dept.

Arlington, TX 76019

Based in part by work supported by the National Science Foundation ECS-0322900

SixGe1-x and SixGe1-xOy Films as Sensing Material

• Both SixGe1-x and SixGe1-xOy are conventional semiconductors

• High TCR (~-5%/K) can be obtained with moderate resistivity value (~104 ohm-cm) from a suitable combination of SixGe1-xOy

• Iborra et. al (2002) reported a TCR of

-4.21%/K from RF Sputtered SixGe1-xOy

• García et. al (2004) reported a TCR of -5.1%/K from PECVD a-Si1-xGex:H,F.

Deposition: SixGe1-x and SixGe1-xOy Films

• Cosputtering from Ge + Si regions target.

• RF magnetron Sputtering at 160 W and 10 mTorr pressure.

• SixGe1-x deposited in Ar environment.

• SixGe1-xOy deposited in Ar:O environment.

Resistivity: SixGe1-x

0 10 20 30 40 500

2

4

6

8

10R

esis

tivity

(1

03

-c

m)

Silicon concentration (at. %)

TCR and Activation Energy (Ea)KT

Ea

eRR

0

0

5 108

1 109

1.5 109

2 109

2.5 109

3 109

3.5 109

4 109

-9

-8

-7

-6

-5

-4

180 200 220 240 260 280 300 320 340

Resistance

TCR

Res

ista

nce

()

TC

R (%

/K)

Temperature (K)

TCR and Activation Energy: SixGe1-x

2

2.5

3

3.5

4

4.5

0.1

0.15

0.2

0.25

0.3

0 5 10 15 20 25 30 35 40

TCR (%/K)

Activation Energy (eV)

0 5 10 15 20 25 30 35 40

TC

R (

%/K

)A

ctivation energy (eV)

Silicon concentration (at. %)

Optical Bandgap: SixGe1-x

0.8

0.9

1

1.1

1.2

1.3

0 10 20 30 40 50

Opt

ical

ban

dgap

(eV

)

Silicon concentration (at. %)

Resistivity: SixGe1-xOy

1000

104

105

106

107

108

109

1010

0 5 10 15 20

15% Silicon

30% Silicon

40% Silicon

0 5 10 15 20

Res

istiv

ity

(-c

m)

Oxygen concentration (at. %)

Activation Energy: SixGe1-xOy

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 5 10 15 20

15% Silicon

30% Silicon

40% Silicon

Act

ivat

ion

ener

gy (

eV)

Oxygen concentration (at. %)

TCR: SixGe1-xOy

2

3

4

5

6

7

8

9

0 5 10 15 20

15% Silicon

30% Silicon

40% Silicon

0 5 10 15 20

TC

R (

%/K

)

Oxygen concentration (at. %)

Noise PSD: Si0.15Ge0.85Oy @ 1.79 μA Bias Current

10-13

10-12

10-11

10-10

10-9

10-8

10-7

1 10 100 1000 104 105

y = 0

y = 0.0309

y = 0.034

1 10 100 1000 104 105

Noi

se V

otag

e P

SD

[V

2 /Hz]

Frequency [Hz]

Transmittance: Si0.15Ge0.85Oy

0

20

40

60

80

100

120

500 1000 1500 2000 2500 3000

9% Oxyzen5.5% Oxyzen3.8% Oxyzen3.46% Oxyzen3% Oxyzen0% Oxyzen

Tan

smit

tanc

e (%

)

Wavelength (nm)

Optical Bandgap: SixGe1-xOy

0.6

0.8

1

1.2

1.4

1.6

1.8

0 5 10 15 20

15% Silicon

30% Silicon

40% Silicon

0 5 10 15 20

Opt

ical

ban

dgap

(eV

)

Oxygen concentration (at. %)

X-ray Diffraction (XRD) Pattern for Si0.125Ge0.8365O0.039

0

50

100

150

200

250

0 10 20 30 40 50 60

Inte

nsit

y (a

rb. u

nits

)

2 (deg.)

Energy Dispersive X-Ray Analysis of Si0.1188Ge0.8472O0.034

Film By Scanning Electron Microscope (SEM)

Transmittance: SixGe1-x

0

20

40

60

80

100

120

140

500 1000 1500 2000 2500 3000

0% Silicon15% Silicon30% Silicon40% Silicon

Tra

nsm

itta

nce(

%)

Wavelength (nm)

Transmittance: Glass Substrate used for Depositing SixGe1-xOy and SixGe1-x Thin Films

40

50

60

70

80

90

100

110

120

500 1000 1500 2000 2500 3000

% T

ran

smis

sion

Wavelength

SixGe1-xOy and SixGe1-x : Normalized Hoogie Coefficient for 1/f-noise (αH/N) determined at 10 Hz frequency and other

propertiesSAMPLE Normalized Hooge

parameterαH/N

TCR(%/K)

Activation Energy (Ea)

(eV)

Optical Bandgap (Eg) (eV)

Si0.15Ge0.85 1.70 × 10-10 4.2 0.264 0.91

Si0.099Ge0.871O0.031 4.3 × 10-11 4.4 0.297 0.80

Si0.118Ge0.847O0.034 1.10 × 10-10 4.6 0.310 0.81

Si0.125Ge0.8365O0.039 < 2.58 × 10-8* 5.1 0.324 0.89

Si0.114Ge0.834O0.052 < 2.35 × 10-6* 5.7 0.368 0.89

Si0.172Ge0.736O0.092 < 4.06 × 10-3* 6.7 0.453 1.4

Si0.294Ge0.706 9.55 × 10-11 3.2 0.181 0.89

Si0.269Ge0.692O0.039 3.12 × 10-8 3.5 0.191 0.75

Si0.281Ge0.628O0.092 < 4.17 × 10-4* 4.9 0.336 1.1

Si0.269Ge0.579O0.152 < 3.62 × 10-4* 7.3 0.577 1.2

Si0.427Ge0.573 < 5.08 × 10-10* 2.3 0.138 0.89

Si0.386Ge0.599O0.015 2.45 × 10-10 2.6 0.155 0.86

Si0.425Ge0.524O0.052 < 4.19 × 10-9* 3.4 0.222 0.86

Si0.380Ge0.525O0.095 < 3.36 × 10-7* 4.7 0.304 0.83

Si0.411Ge0.421O0.168 < 1.30 × 10-4* 8.7 0.658 0.87

Ge 2.07 × 10-10 3.7 0.296 0.96

fN

RIS bHv

22