Transcript Research Institute for Technical Physics and Materials

Research Institute for Technical Physics and Materials
Science of the Hungarian Academy of Sciences
GaN heterostructures with diamond and
graphene for high power applications
B. Pécz
Institute for Technical Physics and Materials Science, Centre for Energy Research, Hungarian
Academy of Sciences
MTA TTK MFA, 1121 Budapest, Konkoly-Thege M. u. 29-33, Hungary
Institute for Technical Physics and Materials Science of the
Hungarian Academy of Sciences
E=hc/l
High power devices
optoelectronics
blue LED---> Nobel prize 2014
Isamu Akasaki, Hiroshi Amano
and Shuji Nakamura
Institute for Technical Physics and Materials Science of the
Hungarian Academy of Sciences
Typical HEMT
structure
to 160 GHz
10 W/mm
U.K. Mishra, P. Parikh, Y.F. Wu: AlGaN/GaN HEMTs: An overview of device operation and applications
Institute for Technical Physics and Materials Science of the
Hungarian Academy of Sciences
Thermal conductivity
diamond: reaching 2000 Wm-1°C-1
copper:
400
SiC:
360-490
graphene:
5000
Institute for Technical Physics and Materials Science of the
Hungarian Academy of Sciences
OUTLINE
GaN HEMT grown on diamond
CVD diamond coating for high power
devices
integration of graphene sheets into
nitride devices
Institute for Technical Physics and Materials Science of the
Hungarian Academy of Sciences
Microscopy: Philips CM20 and JEOL 3010 at MFA
FEI Titan Jülich
TEM sample prep.: Ar+ ion milling, Technoorg-Linda ion miller
difficulties in cutting
long process
Institute for Technical Physics and Materials Science of the
Hungarian Academy of Sciences
GaN HEMT grown on diamond
GaN HEMT grown on diamond
Nitrogen RF plasma source MBE growth
5x5 mm large single crystalline diamond pieces
E6 (http://www.e6.com)
with different orientation (100, 110, 111)
GaN grown on diamond
(111)
overview of the entire layer
(left after chemical etching)
Epitaxy:
(0002)GaN//(111)diamond
and
(1010)GaN//(220)diamond.
numerous inversion domains close to the surface
GaN grown on diamond
(110)
overview of the entire layer
(after chemical etching)
interface region
Epitaxy:
(0002)GaN//(022)diamond
and
(1010)GaN//(400)diamond.
GaN grown on diamond
(001)
Near surface region (chemically etched!)
two different domains: [1010] and [1120] zones
common reflection spots in the 0002 direction
interface region
(0002)GaN//(400)diamond and
(1120)GaN//(022)diamond, or (1010)GaN//(022)diamond
GaN grown on diamond
(001)
(111)
IDs are formed already on the surface of diamond during the AlN growth.
GaN grown on diamond
(111)
Nitridation supressed the formation of IDs.
60 min at 150oC
B. Pécz et al.
Diamond & Related
Materials 34 (2013) 9–12
FEI Titan
GaN grown on diamond
110
Nitridation supressed
the formation of IDs.
N-polarity is determined
by CBED
Polarity of the grown layer
 GaN short vector points to the surface (N-polarity)
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
Recipe can give us GaN on poly-diamond as well
reasonable quality: (002): FWHM=1.92 deg
(114): FWHM=2.0 deg
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
AlGaN/GaN HEMT Grown by Nitride MBE on (111) Diamond
M. Alomari et al.; Electronic Lett., 46 (2010), 299
diamond film grown over InAlN/GaN HEMT
Sample preparation
• Deposition of passivating SiO2/SiN film
• Deposition of a thin amorphous Si layer (conductivity is
necessary for BEN)
• Growth of diamond by hot filament CVD technique (Tfilament =
2200 C)
from CH4/H2 gas mixture (0.3-0.75 %, p = 1.5-3 kPa)
BEN (bias enhanced nucleation) at 700-800 C
Diamond growth at 700 C substrate temperature
Duration: about 50 hours (~5 m diamond)
diamond film grown over InAlN/GaN HEMT
diamond film grown over InAlN/GaN HEMT
The principal phases at the interface (GaN and polycrystalline
Si and diamond) are identified by electron diffraction.
The lateral grain size of the polycrystalline diamond is in the
order of 100 nm.
diamond film grown over InAlN/GaN HEMT
High resolution TEM pictures of the nucleation zone between the Si
and diamond films show plenty of cubic SiC nanoparticles
embedded in an amorphous phase. The growth of the diamond film
starts in this region, too.
diamond film grown over InAlN/GaN HEMT
TEM image and electron diffraction pattern of diamond grown
over an InAlN/GaN HEMT structure (nucleated at 800 C)
diamond film grown over InAlN/GaN HEMT
Sample preparation
Growth conditions
High resolution electron micrograph of the of the InAlN/GaN
heterostructure with the passivating amorphous SiO2 film
deposited on top.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
Alomari M, Dipalo M, Rossi S, Diforte-Poisson M-A, Delage S, Carlin J-F, Grandjean N, Gaquiere
C, Tóth L, Pécz B, Kohn E
Diamond and Related Materials, 20, 2011, Pages 604–608
Optimizing Near-Interface Thermal Conductivity of NCD Thin Films
parameter
time (h:m)
Heat up
BEN
Growth
Cool down
00:40
02:00
Pressure (kPa)
1.5
1.5
1.5
1.5
H2 (sccm)
400
400
400
400
0
1.0
0.2 to 0.6
0
T_filam (°C)
from RT ↑
2130
2130
↓ to RT
T_sub (°C)
from RT ↑
830
825
↓ to RT
V_grid (V)
0
45
0
0
V_bias (V)
0
-200
0
0
CH4 (%)
variable
00:40
Thermal barrier resistance is high
–
–
–
•
reduced interfacial roughness (RMS now in the nm-range) with lower density of pits due to lessaggressive H-plasma etching CH4/H2 ratio was increased substrate T was decreased to 750oC.
a transition zone 10 to 20 nm thick
Minimum TBR of 3 x 10-9 m2 K W-1 (> one order of magnitude lower) with an average value of 5 x
10-9 m2 K W-1 (one order of magnitude improvement)
An alternative strategy to mitigate the surface roughening consists in coating the substrate
with amorphous Si interlayer (a-Si) thin enough to be consumed during BEN (e.g. 10 nm),
thus broadening the application essentially to non-Si substrates.
Nucleation region /3: HRTEM of the sample with a-Si interlayer
The interface diamond/Si
[HRTEM]
In this sample:
•
The transition zone has thickness
below 10 nm
•
SiC grains were clearly identified,
with size of 1-2 nm
•
The electron diffraction pattern
shows only the single crystal Si
pattern and the diamond phase.
No polycrystalline or amorphous
Si phases are visible (the regular
lattice of strong diffraction spots
all belong to the Silicon single
crystal substrate).
Nucleation region: HRTEM of the sample with a-Si interlayer
The interface diamond/Si
[HRTEM]
Interface properties
are optimized.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
integration of graphene sheets into nitride devices
Direct growth onto graphene failed.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
smooth surface
dislocation density
~3 x 109 cm-2
A. Kovács, M. Duchamp, R.E. Dunin-Borkowski, R. Yakimova, P. L. Neumann, H. Behmenburg, B. Foltynski, C.
Giesen, M. Heuken and B. Pécz: Graphoepitaxy of High-Quality GaN Layers on Graphene/6H–SiC, Advanced
Materials Interfaces, 2 (2015) DOI: 10.1002/admi.201400230
AlN growth on continuous graphene
Al and Si EDXS maps superimposed
onto a HAADF STEM image
HAADF STEM image, Si, C and Al EDXS maps recorded using a FEI Titan ChemiSTEM at 200 kV.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
typically 3 layers of graphene, but sometimes 5 are observed
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
BF
DF
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
AlN
AlN
GaN GaN
Al and Ga EDXS maps
overlapped on HAADF
STEM image
Al and Ga distribution extracted as a
line-scan EDXS and HAADF STEM
image as reference.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
Images of the control sample deposited without graphene layers on 6HSiC. (a) SEM image of the surface recorded using a secondary electron
detector. (b) Cross-sectional ADF STEM image.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
• lithographically patterned graphene oxide to improve
heat dissipation in light-emitting diodes (LEDs).
N. Han et al., Nat. Comm. 2013, 4, 1452.
• ZnO coating on O2 plasma treated graphene layers
to grow high quality GaN layers
K. Chung, K.C.-H. Lee and G.C. Yi, Science 2010, 330, 655.
• thermal heat-escaping channels from graphene layers
on the top of AlGaN/GaN transistors
Z. Yan, G. Liu, J.M. Khan, A.A. Balandin, Nat. Comm. 2012, 3, 827.
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
Summary:
Device structures are grown successfully on diamond.
Single crystalline GaN can be grown on poly-diamond as well.
Diamond film with columnar microstructure can be grown
by CVD - promising for heat spreading application.
Graphene layers inserted into nitride devices may help the
heat dissipation
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
Acknowledgement:
J. Lábár (MFA), L. Tóth, Á. Barna, P. Neumann, MFA Budapest
M. Alomari, M. Dipalo, S. Rossi, E. Kohn, Ulm University
A. Georgakilas, FORTH, Heraklion, Crete
M-A. di Forte-Poisson, S. Delage, Alcatel-Thales III-V lab
H. Behmenburg, B. Foltynski, C. Giesen, M. Heuken, AIXTRON SE
A. Kovács, R. D. Borkowski, Jülich
R.Yakimova, Linköping University
Research Institute for Technical Physics and Materials Science
of the Hungarian Academy of Sciences
Thank you for your attention!