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15th International Summer School on Crytsal Growth – ISSCG-15
New trends and challanges in crystal
growth in scientific and commercial
aspects (semiconductors world)
Mike Leszczynski Institute of High Pressure Physics UNIPRESS
And
TopGaN Lasers, Ltd.
Warsaw, Poland
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Abstract
The presentation shows two main new semiconductors: GaN and SiC which
are and will be revolutionizing many areas of the everyday life and
technology. GaN-based optoelectronic devices: white LEDs, laser diodes
emitting from uv to green will soon form new markets of laser tv, „last mile”
telecommunication, water purification, bio-hazardous material detection,
and many others. Both, GaN- and SiC-based electronic devices will replace
many based on silicon, allowing to achieve higher frequencies and power of
transistor operation.
Unfortunately, both GaN and SiC materials are very difficult to be grown
because of their high metling points and other thermodynamic properties. It
will be shown, how lateral patterning helps to overcome many problems with
crystallographic quality of the substrates and the epi-wafers.
Special attention will be paid to the GaN and SiC off-cut substrates, what
changes significantly the properties of the epi structures grown on them.
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Unipress and TopGaN
One of the largest European group involved in research
on GaN-based semiconductors
60 scientists, bulk GaN growth, 9 epitaxial systems, laser
diode processing
15 EU Projects, 10 National Projects on Nitride
Semiconductors
Many patented and proprietary technologies
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Some pictures from Unipress/TopGaN lab
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Semiconductor device markets
Based on Si: around Eur 90 billion OLD TREND
On GaN: around Eur 15 billion NEW TREND
On GaAs: around Eur 5 billion OLD TREND
On SiC: around Eur 0.5 billion NEW TREND
On graphene: to be NEW TREND (shown by Jacek
Majewski)
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Main properties of semiconductors
GaAs, GaN – direct band gap
Si, SiC- indirect (low efficiency of optoelectronic devices)
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Outline
Main new markets
GaN technology (presentation in collaboration with TopGaN
and Unipress)
SiC technology (presentation in collaboration with SiCrystal,
NovaSiC and LPE- Partners in EU LAST POWER project)
Some technological issues
Growth on prepatterned substrates
Off-cut substrates
Elimination of structural defects
Growth of ternary substrates
Large wafers
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
GaN technology
Applications
Present: White LEDs and BluRay
Future: RGB projectors, „Last mile” communication, car
headlights, high-frequency/high-power electronics
Growth on foreign substrates
GaN bulk substrates
Growth on off-cut GaN substrates
Growth of InGaN quantum wells
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Amano and Akasaki (Meijo
University)
At the end of 80-ties of XX
century:
Growth on sapphire
P-doping
Shuji Nakamura (Nichia)
First commercial blue LEDs 1992
First LDs 1996
Strong Japanese domination in GaN technology
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 10
WHITE LEDs
Biggest manufacturers:
Nichia (Japan), OSRAM
(Germany), Lumileds, Cree
(USA)
Market in 2020: Eur 30-60 bln
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
BluRay based on 405 nm laser diodes Manufacturers:
Nichia
Sony
Sanyo
Matsushita
(Japan),
100 Mln pcs in 2012
No further growth
Decrease soon!
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 12
Painting (color projection) should be done using clean paints
In plasma TV, LED TV, color filtering, we „paint” with „dirty” R&G&B emitters
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Only Laser Projection can give a
color resolution like in Nature
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Laser projectors:
Pico
Cinema
Television
3D possible without goggles!!!
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
„Last mile” Tbit/sec communication with
plastic fibres and 480-500 nm laser diodes
Buildings
Cars
Airplanes
Ships
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
GaN-based semiconductors:
Much more difficult to be grown than
Si, GaAs, InP
Melting point: Above 2800 K, 60 kbar
No growth from the melt
Decomposition at 1 bar:
GaN around 1300 K
InN around 800 K
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Almost all LED GaN-based structures are grown
on sapphire or silicon
Dislocation density of about 5x109 cm-2
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Trick with LT
buffer layer
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 19
For laser diodes, it is necessary to have a lower
dislocation density
S. Uchida et al. Sony
Shiroishi Semicond. Inc
IEEE J. of Selected Topics in
Quantum Electronics 9, no 5,
(2003)1252.
Our data
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
SUMITOMO- leader in GaN substrate growth
http://global-sei.com/news/press/10/10_25.html
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Ammonothermal growth
2-inch
n-type do 2x1019 cm-3
p-type,
TDD=5x104 cm-2
R=100 m
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 22
HVPE + HNP – combined method of TopGaN
High Nitrogen
Pressure Overgrowth
Hydride Vapour Phase Epitaxy:
Fast growth, large dimensions
+
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 1.5 inch HNPS-GaN 330 µm T
t=500 h
a b c
nowo wzrośnięty
HNPS-GaN
GaN substrates from
Multi-feed-seed-method
10 kbar, 1600oC, growth from N solution in
Ga
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 24
GaN-based laser diodes- main issues
p- doping InGaN QWs- In-segregation, electric built-in fields AlGaN- cladding, lattice mismatch Bulk GaN substrate
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Laser diode epitaxial structure: TEM topograph
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 26
Lattice mismatch Green gap
Electric field
In segregation in InGaN
P-doping And others!!!
Droop
Problems in GaN technology
holes
electrons
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Elimination of
cracking and
bowing
No AlN mask
With AlN mask 15 10 5 3 m
Defect density: window <106/cm2 mask 1010/cm2
AlGaN 27% 220 nm
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Motivation of using off-oriented substrates:
Better/different electrical, optical, structural,
morphological, properties of AlGaN, InGaN, InAlN
Cutting/polishing- expensive Lateral patterning
(patented)
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 29
Misorientation of 0.5-1 degree desired because of better morphology
AFM- GaN layers grown at high temperature
Misorientation: 0.2 degree 0.6 degree
Higher misorientation (above 1 degree): step condensation
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 30
P-doping
Hole concentration in GaN:Mg I-V LD characteristics No difference in Mg and H concentration (SIMS)
0 5 10 15 20
0
1
2
3
4
5
6
7
8
9
10
laser
diod
e vo
ltage
[V]
current density (kA/cm2)
miscut 1 deg
miscut 0.2 deg
0,0 0,5 1,0 1,5 2,0 2,50,0
5,0x1017
1,0x1018
NT1388
Ho
le c
arr
ier
co
nce
ntr
atio
n
p [
cm
-3]
Misorientation angle [deg.]
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 31
Morphology of InGaN layers grown on GaN substrates of different misorientation, Tgrowth = 820oC
0.2 degree 0.8 degree 1.8 degree
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
In incorporation into InGaN layers versus
GaN substrate misorientation
Lower indium incorporation into InGaN for
off-oriented GaN substrate
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
The same mechanism as in indium incorporation into
InGaN versus growth rate in step-flow mode
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Lateral patterning to vary the misorientation across
the wafer- multicolour arrays of laser diode stripes
12 nm difference in lasing
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
InGaN growth very difficult
Active region of all optoelectronic devices
emitting in visible region
Low growth temperature and large lattice
mismatch:
Point defects (including oxygen)
Indium segregation
3D growth
Mismatch defects (dislocations, pits)
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
In content – 14%
In content – 18%
In content – average 22%
420 440 460 480 500 520 540
0.0
0.2
0.4
0.6
0.8
1.0
no
rma
lize
d in
ten
sity
[nm]
TGR
= 800oC
TGR
= 770oC
TGR
= 730oC
TGR=800oC : =455nm fwhm=27nm
TGR=770oC : =506nm fwhm=29nm
TGR=730oC : =509nm fwhm=41nm
XRD:
31 32 33 34 35 36 37 38
1
10
100
1000
10000
100000
1000000
inte
nsity [
a.u
.]
2theta [deg.]
TGR
=800oC
TGR
=770oC
TGR
=730oC
PL- Photoluminescence (He-Cd laser 325 nm, cw):
QW growth temperature
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
XRD
Hydrogen effectively removes In and widens QBs
but also affects QWs:
removes In and makes them narrower.
0 10 20 30 402
3
4
5
6
7
8
9
10
11
12
13
14
15
QW
QB
wid
th [nm
]
H2 [%]
0 10 20 30 400
1
2
3
4
5
6
7
8
9
10
11
12
13
14
QW
QB
In [%
]
H2 [%]
Influence of H2 during QB growth
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
T=905oC In – 16%
=463nm
At high temperature satellite peaks becomes much more broader and
disappear :
QWs degradation occurs
T=880oC In – 18%
=463nm
T=830oC In – 18%
=463nm
T=930oC In – ?
=463nm
PL intensity decrease 31 32 33 34 35 36 37 38
0,1
1
2theta/ [deg.]
inte
nsity [
a.u
.]
Motivation: QWs must be overgrown with p-type layers
commonly fabricated at high temperatures
TGr of p-type layers
P-type growth
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Electronics
High Electron
Mobility Transistors
(HEMTs)
based on 2DEG
Sensors of liquids
and gases
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
GigaHertz and TeraHertz area
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
THz emitters and detectors
0 10 20 30 40 50 60 700
10
20
30
40
50
60
70
80
90
X Axis (mm)
Y A
xis
(mm
)
0
0.02100
0.04200
0.06300
0.08400
0.1050
0.1260
0.1470
0.1680
0.1890
0.2100
Control of
water in
plants
Quality control in
manufacturing
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 42
GaN and SiC electronics:
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
GaN GHz and THz
Electronic devices by power and frequency
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
SiC technology
Applications in SiC electronics
Growth of SiC crystals
SiC epitaxy
GaN epitaxy on SiC crystals
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
It is difficult
to grow SiC
crystal without
polytyping
And more than 240 others!!!
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
It is even more difficult to grow SiC crystal
without micropipes
1) open core super screw
dislocations that propagate
along the C-axis from the
seed crystal during growth .
2) Contaminant particles
introduced during the growth
process
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
One of possible
mechanisms of
micropipe formation
(after MaxMile
Technologies)
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Philip G. Neudeck and J. Anthony Powell
For many years, micropipes have been a main
obstacle in development of SiC based power
electronics
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Quality results: Seed 155mm
High crystalline quality of 155 seed SiC shown by low FWHM close to equipment resolution. Next step: Increase diameter to 160mm.
2013: CREE and SiCrystal manufacture 6 inch SiC
substrates with no micropipes!!!
~ ~ FWHM = 13.61 arcsec
High resolution X-ray
diffraction
Crossed
polarizers
MPD
mapping 2 deg-off – a new standard for SiC epitaxy?
So far 4 deg off and 8 deg off.
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Substrate from SY SiC 4” – 4H – 2°off Si-face CMP (Novasic), C-face optical polished
LPE: 2° off epi Optimization on 4’’ SiC 4H wf
– Mosfet Spec
- Lower epi stacking faults
(ESF) defects density (< 1,7 vs.
4.9 cm-2)
- high percentage of area free of
defects was (95,6%).
- low epi roughness (0,7 nm)
has been reached even in some
region is still high (2.8 -1,5 nm).
- Better epi thickness uniformity
(± 1,5%)
- Worse epi doping uniformity
was observed (15-22% VS USL
10%).
- some striped epi surface
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
2 deg off SiC substrates
Common platform for SiC-based devices
and GaN-based devices
1.Monolithic integration
2. Cheaper SI SiC substrates (conductive
SiC substrate with insulating homoepitaxial
layer) for high-frequency HEMTs based on
GaN
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
AlN
GaN undoped
1.5 um
AlN 1nm
AlGaN 20 nm
Cap GaN 2nm
SiC
TG2136 0°-off
TG2134 1°-off
TG2135 2°-off
XRD: TG2134 – Al0.22
GaN, 22 nm
TG2135 – Al0.21
GaN, 22 nm
TG2136 – Al0.21
GaN, 21 nm
HEMT wafers on off-cut SiC
32 33 34 35 36 37
100
101
102
103
104
105
106
HEMT on SiC
inte
nsity [cp
s]
2theta [deg]
0o offcut, tg2136
1o offcut, tg2134
2o offcut, tg2135
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Comparison of roughness for HEMT epi-
structures for various off-cut of SiC substrates
Ra = 0.19 nm 0.77 nm 1.08 nm
AFM scans 3x3 mm2
Dislocation density 108 cm-2 (can be lower for off-cut substartes, but
in that case, roughness larger
0 deg 1 deg 2deg off
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Electrical parameters of HEMT epi
wafers on off-cut SiC substrates
Off-cut
(deg)
n (1013cm-
2) Hall
(cm2/Vs)
Hall
(W)
0 1.26 1280 365
1 1.4 1323 332
2 1.03 1413 429
No significant difference in electrical parameters
15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE
Concluding remarks
1) GaN and SiC single crystals and epi-wafers pave the
way to a number of new markets:
Electric cars
Gigahertz and terahertz emitters and detectors
Laser TV, picoprojectors, cinema, telebeams, also 3D!!!
„Last mile” communication
And many others...
2) (AlGaIn)N and SiC are still in the infancy stage of
development, as they are very difficult to be grown,
processed and examined.