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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.

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Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences

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  1. 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 Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences

  2. 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

  3. 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

  4. Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences Thermalconductivity diamond: reaching 2000 Wm-1°C-1 copper: 400 SiC: 360-490 graphene: 5000

  5. Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences OUTLINE

  6. 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

  7. GaN HEMT grown on diamond Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences 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)

  8. 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

  9. 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.

  10. GaN grown on diamond (001) Near surface region (chemically etched!) two different domains: [1010] and [1120] zones common reflection spots in the 0002 direction (0002)GaN//(400)diamond and interface region (1120)GaN//(022)diamond, or (1010)GaN//(022)diamond

  11. GaN grown on diamond (001) (111) IDs are formed already on the surface of diamond during the AlN growth.

  12. 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

  13. GaN grown on diamond 110 Nitridation supressed the formation of IDs. N-polarity is determined by CBED

  14. Polarity of the grown layer GaN short vector points to the surface (N-polarity)

  15. 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

  16. 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

  17. 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)

  18. diamond film grown over InAlN/GaN HEMT

  19. 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.

  20. 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.

  21. 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)

  22. 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.

  23. 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

  24. Optimizing Near-Interface Thermal Conductivity of NCD Thin Films Thermal barrier resistance is high • 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) • 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.

  25. 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).

  26. Nucleation region: HRTEM of the sample with a-Si interlayer The interface diamond/Si [HRTEM] Interface properties are optimized.

  27. integration of graphene sheets into nitride devices Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences Direct growth onto graphene failed.

  28. 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

  29. 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.

  30. Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences typically 3 layers of graphene, but sometimes 5 are observed

  31. Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences BF DF

  32. 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.

  33. 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.

  34. Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences • lithographicallypatternedgrapheneoxidetoimprove • heatdissipation in light-emittingdiodes (LEDs). • N. Han et al., Nat. Comm. 2013, 4, 1452. • ZnOcoating on O2plasmatreatedgraphenelayers • togrow high qualityGaNlayers • K. Chung, K.C.-H. Lee and G.C. Yi, Science2010, 330, 655. • thermal heat-escapingchannelsfromgraphenelayers • on the top ofAlGaN/GaNtransistors • Z. Yan, G. Liu, J.M. Khan, A.A. Balandin, Nat. Comm. 2012, 3, 827.

  35. 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

  36. 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 • Kovács, R. D. Borkowski, Jülich R.Yakimova, Linköping University

  37. Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences Thank you for your attention!

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