Effect of AlN Dielectric Layer on Growth of Diamond Passivation Film on GaN Surface

doi:10.16553/j.cnki.issn1000-985x.2025.0030

Abstract

Abstract: The growth of diamond passivation film on GaN surface can be used to improve the heat transfer ability of devices， and enhance the power characteristics and reliability of devices. The dielectric layer between GaN and diamond layers is crucial for achieving high-quality diamond on GaN surface. This study used atomic layer deposition （ALD） technology to pre-deposit a 10 nm crystalline/amorphous mixed AlN dielectric layer on the surface of GaN， and achieved high-density electrostatic self-assembly seeding on the AlN layer through surface terminal controlled diamond suspension； subsequently， an optimized microwave plasma chemical vapor deposition （MPCVD） process was used to grow nanocrystalline diamond（NCD）films with a thickness of approximately 120 nm. The surface oxygen terminal regulated nanodiamond suspension can achieve high-density seeding on the surface of AlN dielectric layer. Combined with gradient methane MPCVD diamond growth process， NCD thin films with high crystallinity， low roughness （Ra=15.2 nm）， and low residual stress （0.84 GPa） were prepared. Time domain thermal reflection（TDTR）measurements indicate that the thermal conductivity of NCD film is approximately 123.85 W·m^-1·K^-1. The effective thermal boundary resistance （TBR_eff） between GaN and NCD is （9.78±0.27） m²·K·GW^-1. Transmission electron microscopy （TEM） analysis shows that， AlN dielectric layer effectively protects GaN from plasma etching and achieves a smooth interface between diamond and GaN. This study shows that using thin ALD AlN as the dielectric layer for growing diamond on GaN surface can achieve electrostatic self-assembly with oxygen terminated diamond seeds， thereby increasing diamond nucleation density. Then， through gradient methane diamond deposition process， high-quality NCD films can be deposited on GaN and the thermal boundary resistance between diamond and GaN can be reduced.

Key words: nanocrystalline diamond; GaN; AlN dielectric layer; thermal conductivity; thermal boundary resistance; atomic layer deposition; electrostatic self-assembly seeding

CLC Number:

TN386

LIANG Lifeng, YU Xinxin, LI Zhonghui, LIU Jinlong, LI Chengming, WANG Xinhua, WEI Junjun. Effect of AlN Dielectric Layer on Growth of Diamond Passivation Film on GaN Surface[J]. Journal of Synthetic Crystals, 2025, 54(8): 1417-1425.

Figures/Tables 8

Fig.1 Schematic diagram of the preparation process for the passivation layer of nanocrystalline diamond

Fig.2 Comparison of Zeta potentials of Un-NDs， O-NDs， AlN and FTIR test results before and after air annealing of NDs. （a） Zeta potential test results of Un-NDs， O-NDs and AlN；（b） FTIR of NDs before and after air annealing

Fig.3 Schematic diagram of electrostatic self-assembly process between AlN surface and O-NDs due to mutual attraction

Fig.4 Multi-dimensional characterization of surface morphology and composition structure of diamond passivation layer （including comparison with AlN surface morphology before deposition）. （a） SEM image of the surface morphology of the diamond passivation layer；（b） AFM image of diamond passivation layer surface；（c） SEM image of AlN surface morphology before diamond deposition；（d） Raman spectroscopy of diamond passivation layer

Fig.5 TDTR characterization and layer thickness dependent sensitivity analysis of thermal conductivity at Diamond/GaN interface. （a） TDTR test data fitting curve；（b） sensitivity of Diamond/GaN ITC and layer thickness

Table 1 TDTR test results

Layer	Thickness	TC/（W·m^-1·K^-1）	TBR_eff/（m²·K·GW^-1）
Aluminum	100 nm	237	—
Al/Diamond	—	—	21.17
NCD	120 nm	123.85	—
Diamond/GaN	—	—	9.78±0.27
GaN	2 μm	205	—
SiC	500 μm	400	—

Fig.6 HRTEM image of AlN on the substrate surface

Fig.7 Characterization of interface microstructure and element distribution of Diamond/AlN/GaN composite structure based on TEM and EDS. （a） TEM image of NCD membrane fracture；（b） TEM image at the Diamond/AlN/GaN interface；（c） EDS at Diamond/AlN/GaN interface

References 28

[1]	CAO L N， WANG J S， HARDEN G， et al. Experimental characterization of impact ionization coefficients for electrons and holes in GaN grown on bulk GaN substrates［J］. Applied Physics Letters， 2018， 112（26）： 262103.
[2]	PENGELLY R S， WOOD S M， MILLIGAN J W， et al. A review of GaN on SiC high electron-mobility power transistors and MMICs［J］. IEEE Transactions on Microwave Theory and Techniques， 2012， 60（6）： 1764-1783.
[3]	BAR-COHEN A， MAURER J J， ALTMAN D H. Embedded cooling for wide bandgap power amplifiers： a review［J］. Journal of Electronic Packaging， 2019， 141（4）： 040803.
[4]	POMEROY J W， UREN M J， LAMBERT B， et al. Operating channel temperature in GaN HEMTs： DC versus RF accelerated life testing［J］. Microelectronics Reliability， 2015， 55（12）： 2505-2510.
[5]	CHU K K， CHAO P C， DIAZ J A， et al. S2-T4： low-temperature substrate bonding technology for high power GaN-on-diamond HEMTs［C］// 2014 Lester Eastman Conference on High Performance Devices （LEC）. August 5-7， 2014， Ithaca， NY， USA. IEEE， 2014： 1-4.
[6]	JESSEN G H， GILLESPIE J K， VIA G D， et al. AlGaN/GaN HEMT on diamond technology demonstration［C］// 2006 IEEE Compound Semiconductor Integrated Circuit Symposium. November 12-15， 2006， San Antonio， TX， USA. IEEE， 2006： 271-274.
[7]	HIRAMA K， KASU M， TANIYASU Y. RF high-power operation of AlGaN/GaN HEMTs epitaxially grown on diamond［J］. IEEE Electron Device Letters， 2012， 33（4）： 513-515.
[8]	ARIVAZHAGAN L， JARNDAL A， NIRMAL D. GaN HEMT on Si substrate with diamond heat spreader for high power applications［J］. Journal of Computational Electronics， 2021， 20（2）： 873-882.
[9]	ZHANG H， GUO Z X， LU Y F. Enhancement of hot spot cooling by capped diamond layer deposition for multifinger AlGaN/GaN HEMTs［J］. IEEE Transactions on Electron Devices， 2020， 67（1）： 47-52.
[10]	SEELMANN E M， MEISEN P， SCHAUDEL F， et al. Heat-spreading diamond films for GaN-based high-power transistor devices［J］. Diamond and Related Materials， 2001， 10（3/4/5/6/7）： 744-749.
[11]	MIRMIRA S R， FLETCHER L S. Review of the thermal conductivity of thin films［J］. Journal of Thermophysics and Heat Transfer， 1998， 12（2）： 121-131.
[12]	SLACK G A， TANZILLI R A， POHL R O， et al. The intrinsic thermal conductivity of AlN［J］. Journal of Physics and Chemistry of Solids， 1987， 48（7）： 641-647.
[13]	YATES L， ANDERSON J， GU X， et al. Low thermal boundary resistance interfaces for GaN-on-diamond devices［J］. ACS Applied Materials & Interfaces， 2018， 10（28）： 24302-24309.
[14]	JIA X， WEI J J， KONG Y C， et al. The influence of dielectric layer on the thermal boundary resistance of GaN-on-diamond substrate［J］. Surface and Interface Analysis， 2019， 51（7）： 783-790.
[15]	ONN D G， WITEK A， QIU Y Z， et al. Some aspects of the thermal conductivity of isotopically enriched diamond single crystals［J］. Physical Review Letters， 1992， 68（18）： 2806-2809. PMID
[16]	ZHU R H， MIAO J Y， LIU J L， et al. High temperature thermal conductivity of free-standing diamond films prepared by DC arc plasma jet CVD［J］. Diamond and Related Materials， 2014， 50： 55-59.
[17]	CHO J， LI Z J， BOZORG G E， et al. Improved thermal interfaces of GaN-diamond composite substrates for HEMT applications［J］. IEEE Transactions on Components， Packaging and Manufacturing Technology， 2013， 3（1）： 79-85.
[18]	BOPPART H， VAN-STRAATEN J， SILVERA I F. Raman spectra of diamond at high pressures［J］. Physical Review B， 1985， 32（2）： 1423-1425. PMID
[19]	MALAKOUTIAN M， FIELD D E， HINES N J， et al. Record-low thermal boundary resistance between diamond and GaN-on-SiC for enabling radiofrequency device cooling［J］. ACS Applied Materials & Interfaces， 2021， 13（50）： 60553-60560.
[20]	MALAKOUTIAN M， LAURENT M A， CHOWDHURY S. A study on the growth window of polycrystalline diamond on Si₃N₄-coated n-polar GaN［J］. Crystals， 2019， 9（10）： 498-498.
[21]	FERRARI A C， ROBERTSON J. Raman spectroscopy of amorphous， nanostructured， diamond-like carbon， and nanodiamond［J］. Philosophical Transactions Series A， Mathematical， Physical， and Engineering Sciences， 2004， 362（1824）： 2477-2512.
[22]	ZENG L Y， PENG H Y， WANG W B， et al. Nanocrystalline diamond films deposited by the hot cathode direct current plasma chemical vapor deposition method with different compositions of CH₄/Ar/H₂ gas mixture［J］. The Journal of Physical Chemistry C， 2008， 112（5）： 1401-1406.
[23]	YANG Q， CHEN W， XIAO C， et al. Low temperature synthesis of diamond thin films through graphite etching in a microwave hydrogen plasma［J］. Carbon， 2005， 43（12）： 2635-2638.
[24]	AJIKUMAR P K， GANESAN K， KUMAR N， et al. Role of microstructure and structural disorder on tribological properties of polycrystalline diamond films［J］. Applied Surface Science， 2019， 469： 10-17.
[25]	KOREPANOV V I， HAMAGUCHI H O， OSAWA E， et al. Carbon structure in nanodiamonds elucidated from Raman spectroscopy［J］. Carbon， 2017， 121： 322-329.
[26]	YOSHIKAWA M， MORI Y， OBATA H， et al. Raman scattering from nanometer-sized diamond［J］. Applied Physics Letters， 1995， 67（5）： 694-696.
[27]	YUAN C， HANUS R， GRAHAM S. A review of thermoreflectance techniques for characterizing wide bandgap semiconductors' thermal properties and devices’ temperatures［J］. Journal of Applied Physics， 2022， 132（22）： 220701.
[28]	SATURDAY L， WILSON L， RETTERER S， et al. Thermal conductivity of nano- and micro-crystalline diamond films studied by photothermal excitation of cantilever structures［J］. Diamond and Related Materials， 2021， 113： 108279.