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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. PéczInstitute for Technical Physics and Materials Science, Centre for Energy Research, Hungarian
Academy of SciencesMTA TTK MFA, 1121 Budapest, Konkoly-Thege M. u. 29-33, Hungary
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Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
High power devices optoelectronicsblue LED---> Nobel prize 2014
Isamu Akasaki, Hiroshi Amano and Shuji Nakamura
E=hc/
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Typical HEMTstructureto 160 GHz10 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
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Thermal conductivitydiamond: reaching 2000 Wm-1°C-1
copper: 400SiC: 360-490graphene: 5000
Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
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Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
OUTLINE
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Microscopy: Philips CM20 and JEOL 3010 at MFA
FEI Titan Jülich
TEM sample prep.: Ar+ ion milling, Technoorg-Linda ion millerdifficulties in cuttinglong process
Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
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Nitrogen RF plasma source MBE growth
5x5 mm large single crystalline diamond pieces E6 (http://www.e6.com)
with different orientation (100, 110, 111)
Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
GaN HEMT grown on diamondGaN HEMT grown on diamond
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GaN grown on diamond (111)
overview of the entire layer(left after chemical etching)
numerous inversion domains close to the surface
Epitaxy:(0002)GaN//(111)diamond
and (1010)GaN//(220)diamond.
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GaN grown on diamond (110)
overview of the entire layer (after chemical etching)
interface regionEpitaxy:
(0002)GaN//(022)diamondand (1010)GaN//(400)diamond.
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GaN grown on diamond (001)
interface region
Near surface region (chemically etched!)
two different domains: [1010] and [1120] zonescommon reflection spots in the 0002 direction
(0002)GaN//(400)diamond and
(1120)GaN//(022)diamond, or (1010)GaN//(022)diamond
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GaN grown on diamond (001) (111)
IDs are formed already on the surface of diamond during the AlN growth.
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GaN grown on diamond (111)
Nitridation supressed the formation of IDs.60 min at 150oC
FEI Titan
B. Pécz et al. Diamond & Related Materials 34 (2013) 9–12
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GaN grown on diamond 110
Nitridation supressed the formation of IDs.
N-polarity is determinedby CBED
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Polarity of the grown layer
GaN short vector points to the surface (N-polarity)
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Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
Recipe can give us GaN on poly-diamond as wellreasonable quality: (002): FWHM=1.92 deg
(114): FWHM=2.0 deg
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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
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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 temperatureDuration: about 50 hours (~5 m diamond)
diamond film grown over InAlN/GaN HEMT
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diamond film grown over InAlN/GaN HEMT
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diamond film grown over InAlN/GaN HEMT
The lateral grain size of the polycrystalline diamond is in the order of 100 nm.
The principal phases at the interface (GaN and polycrystalline Si and diamond) are identified by electron diffraction.
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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.
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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)
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diamond film grown over InAlN/GaN HEMT
Sample preparationGrowth conditions
High resolution electron micrograph of the of the InAlN/GaN heterostructure with the passivating amorphous SiO2 film deposited on top.
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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
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Thermal barrier resistance is high
• 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.
–reduced interfacial roughness (RMS now in the nm-range) with lower density of pits due to less-aggressive 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)
parameter Heat up BEN Growth Cool down
time (h:m) 00:40 02:00 variable 00:40
Pressure (kPa) 1.5 1.5 1.5 1.5
H2 (sccm) 400 400 400 400
CH4 (%) 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
Optimizing Near-Interface Thermal Conductivity of NCD Thin Films
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Nucleation region /3: HRTEM of the sample with a-Si interlayer
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).
The interface diamond/Si[HRTEM]
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Nucleation region: HRTEM of the sample with a-Si interlayer
The interface diamond/Si[HRTEM]
Interface properties are optimized.
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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.
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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
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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.
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Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
typically 3 layers of graphene, but sometimes 5 are observed
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Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
BF
DF
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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.
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Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
Images of the control sample deposited without graphene layers on 6H-SiC. (a) SEM image of the surface recorded using a secondary electron detector. (b) Cross-sectional ADF STEM image.
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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 transistorsZ. Yan, G. Liu, J.M. Khan, A.A. Balandin, Nat. Comm. 2012, 3, 827.
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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 grownby CVD - promising for heat spreading application.
Graphene layers inserted into nitride devices may help theheat dissipation
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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
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Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences
Thank you for your attention!