图形化蓝宝石衬底表面原位处理对GaN外延薄膜的影响
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摘要
采用预铺Ga或NH_3氮化等方式原位处理图形化蓝宝石衬底(PSS)表面,然后外延生长了GaN薄膜,研究了PSS表面预处理对GaN薄膜表面形貌、晶体质量以及残余应力的影响。结果显示,PSS经过预铺Ga后生长的GaN薄膜具有平滑的表面和清晰平直的原子台阶,且位错密度最低;氮化后生长的GaN薄膜原子台阶较宽,螺型位错密度较低;衬底未经表面处理生长的GaN薄膜,原子台阶模糊,位错密度最高;同时,与氮化或未经预处理的方法相比,经过预铺Ga的方式预处理PSS表面后生长的GaN薄膜残余应力最小。分析认为,预铺Ga、氮化等方式处理衬底表面,改变了PSS微结构,有利于生长表面平滑、晶体质量高、残余应力小的GaN薄膜。
The patterned sapphire substrate(PSS) surface was treated in-situ by pre-Ga or NH_3 nitriding, and then GaN films were grown epitaxially. The effects of the PSS surface pretreatment on the surface morphology, crystal quality and residual stress of GaN films were studied. The results show that the GaN film grown on the PSS after pre-Ga treatment has smooth surface, straight atomic steps and the lowest dislocation density. GaN films grown after nitriding treatment have wider atomic steps and lower screw dislocation density. GaN films grown on the substrate without surface treatment have a fuzzy atomic step and the highest dislocation density. At the same time, compared with nitriding or non-pretreatment methods, GaN films grown after pre-Ga treatment of the PSS surface have the smallest residual stress. The analysis shows that pre-Ga and nitriding treatment of the substrate surface have changed the microstructure of the PSS and are conducive to the growth of GaN films with smooth surface, high crystal quality and low residual stress.
The patterned sapphire substrate(PSS) surface was treated in-situ by pre-Ga or NH_3 nitriding, and then GaN films were grown epitaxially. The effects of the PSS surface pretreatment on the surface morphology, crystal quality and residual stress of GaN films were studied. The results show that the GaN film grown on the PSS after pre-Ga treatment has smooth surface, straight atomic steps and the lowest dislocation density. GaN films grown after nitriding treatment have wider atomic steps and lower screw dislocation density. GaN films grown on the substrate without surface treatment have a fuzzy atomic step and the highest dislocation density. At the same time, compared with nitriding or non-pretreatment methods, GaN films grown after pre-Ga treatment of the PSS surface have the smallest residual stress. The analysis shows that pre-Ga and nitriding treatment of the substrate surface have changed the microstructure of the PSS and are conducive to the growth of GaN films with smooth surface, high crystal quality and low residual stress.
引文
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[2] FANG Y L,FENG Z H,YIN J Y,et al.Ultrathin InAlN/GaN heterostructures with high electron mobility [J].Physica Status Solidi:b,2015,252(5):1006-1010.
[3] FANG Y L,FENG Z H,LI C M,et al.Trap behaviors in AlGaN/GaN based polarization-doped field effect transistors by frequency-dependent conductance-voltage characterizations [J].Superlattices & Microstructures,2015,82:201-206.
[4] BAJO M M,HODGES C,UREN M J,et al.On the link between electroluminescence,gate current leakage,and surface defects in AlGaN/GaN high electron mobility transistors upon off-state stress [J].Applied Physics Letters,2012,101(3):033508-1-033508-4.
[5] HE C G,ZHAO W,ZHANG K,et al.High-quality GaN epilayers achieved by facet-controlled epitaxial lateral overgrowth on sputtered AlN/PSS templates [J].ACS Applied Materials & Interfaces,2017,9(49):43386-43392.
[6] LIANG M,WANG G H,LI H J,et al.Low threading dislocation density in GaN films grown on patterned sapphire substrates [J].Chinese Journal of Semiconductors,2012,33(11):113002-1-113002-4.
[7] CAO W J,BISER J M,EE Y K,et al.Dislocation structure of GaN films grown on planar and nano-patterned sapphire [J].Journal of Applied Physics,2011,110(5):053505-1-053505-4.
[8] 周仕忠,林志霆,王海燕,等.图形化蓝宝石衬底GaN基LED的研究进展 [J].半导体技术,2012,37(6):417-424.ZHOU S Z,LIN Z T,WANG H Y,et al.Research progress of patterned sapphire substrate for GaN-based light-emitting diodes [J].Semiconductor Technology,2012,37(6):417-424 (in Chinese).
[9] 郝跃,张金凤,张进成.氮化物宽禁带半导体材料和电子器件 [M].北京:科学出版社,2013:39-65.
[10] BURTON W K,CABRERA N,FRANK F C.The growth of crystals and the equilibrium structure of their surfaces [J].Philosophical Transactions of the Royal Society:A,1951,243(866):299-358.
[11] MORAM M A,VICKERS M E.X-ray diffraction of III-nitrides [J].Reports on Progress in Physics,2009,72 (3):036502-1-036502-40.
[12] KIM M H,SONE C,YI J H,et al.Changes in the growth mode of low temperature GaN buffer layers with nitrogen plasma nitridation of sapphire substrates [J].Applied Physics Letters,1997,71(9):1228-1230.
[13] PAEK J S,KIM K K,LEE J M,et al.Nitridation of sapphire substrate and its effect on the growth of GaN layer at low temperature [J].Journal of Crystal Growth,1999,200(1/2):55-62.
[14] GRANDJEAN N,MASSIES J,LEROUX M.Nitridation of sapphire:effect on the optical properties of GaN epitaxial overlayers [J].Applied Physics Letters,1996,69(14):2071-2073.
[15] WIDMANN F,FEUILLET G,DAUDIN B,et al.Low temperature sapphire nitridation:a clue to optimize GaN layers grown by molecular beam epitaxy [J].Journal of Applied Physics,1999,85(3):1550-1555.
[16] GRANDJEAN N,MASSIES J.Molecular beam epitaxy growth of nitride materials [J].Materials Science and Engineering:B,1999,59(1/2/3):39-46.
[17] NAMKOONG G,DOOLITTLE W A,BROWN A S,et al.Role of sapphire nitridation temperature on GaN growth by plasma assisted molecular beam epitaxy:part I.impact of the nitridation chemistry on material characteristics [J].Journal of Applied Physics,2002,91(4):2499-2507.
[18] DWIKUSUMA F,KUECH T F.X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy:nitridation mechanism [J].Journal of Applied Physics,2003,94(9):5656-5664.
[19] RYU J H,KATHARRIA Y S,KIM H Y,et al.Stress-relaxed growth of n-GaN epilayers [J].Applied Physics Letters,2012,100(18):181904-1-181904-4.