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1. 华南理工大学理学院物理系 广东省光电工程技术研究开发中心,广东 广州,510640
2. 鹤山丽得电子实业有限公司, 广东 鹤山,529728
收稿日期:2014-04-29,
修回日期:2014-05-20,
纸质出版日期:2014-08-03
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黄华茂, 杨光, 王洪等. 高温预生长对图形化蓝宝石衬底GaN薄膜质量的提高[J]. 发光学报, 2014,35(8): 980-985
HUANG Hua-mao, YANG Guang, WANG Hong etc. Improvement of GaN Thin-film Quality Grown on Patterned Sapphire Substrate by High-temperature Pre-growth Treatment[J]. Chinese Journal of Luminescence, 2014,35(8): 980-985
黄华茂, 杨光, 王洪等. 高温预生长对图形化蓝宝石衬底GaN薄膜质量的提高[J]. 发光学报, 2014,35(8): 980-985 DOI: 10.3788/fgxb20143508.0980.
HUANG Hua-mao, YANG Guang, WANG Hong etc. Improvement of GaN Thin-film Quality Grown on Patterned Sapphire Substrate by High-temperature Pre-growth Treatment[J]. Chinese Journal of Luminescence, 2014,35(8): 980-985 DOI: 10.3788/fgxb20143508.0980.
在图形化蓝宝石衬底生长低温缓冲层之前,通入少量三甲基镓(TMGa)和大量氨气进行短时间的高温预生长,通过改变TMGa流量制备了4个蓝光LED样品。MOCVD外延生长时使用激光干涉仪实时监测薄膜反射率,外延片使用高分辨率X射线衍射(002)面和(102)面摇摆曲线估算位错密度,并使用光致发光谱表征发光性能,制备成芯片后测试了正向电压和输出光功率。结果表明,高温预生长可促进薄膜的横向外延,使得三维岛状GaN晶粒在较小的薄膜厚度内实现岛间合并,有利于降低位错密度,提高外延薄膜质量,LED芯片的输出光功率的增强幅度达29.1%,而电学性能无恶化迹象;但高温预生长工艺中TMGa的流量应适当控制,过量的TMGa导致GaN晶粒过大,将延长岛间合并时间,降低晶体质量。
Before the epitaxy of low-temperature buffer layer
the patterned sapphire substrate was prepared by a pre-growth treatment at a high temperature under a small amount of trimethyl gallium (TMGa) and a great quantity of ammonia (NH
3
). Four types of blue light-emitting diode (LED) wafers were fabricated using different flow-rate of TMGa. The laser interferometer in MOCVD was used to monitor the thin-film reflectance during the epitaxial growth process. The high-resolution X-ray diffraction rocking curves of (002) and (102) crystal faces were utilized to estimate the threading dislocation density. The photoluminescence spectra were measured to feature the light-output performance. Moreover
LED chips were fabricated and tested. It is shown that the pre-growth treatment benefits the lateral growth of three-dimensional GaN islands in epitaxy process and leads to fast coalescence within a small thickness. Thus
the threading dislocation can be suppressed and the quality of epitaxial film would be improved. The enhancement of light-output power of LED chips can be up to 29.1% without degradation of electrical performance. However
the flow rate of TMGa should be tuned carefully
because excess quantity of TMGa would cause a large size of GaN grain crystal
which induces delayed coalescence time and low-quality of epitaxial film.
Han N, Park Y J, Han M, et al. Threading dislocation reduction in epitaxial GaN using V-groove patterned sapphire substrate with embedded silica nanospheres [J]. Mater. Lett., 2014, 123:97-100.
Lin Z Y, Zhang J C, Zhou H, et al. Influence of double AlN buffer layers on the qualities of GaN films prepared by metal-organic chemical vapour deposition [J]. Chin. Phys. B (中国物理:B), 2012, 21(12):126804-1-5 (in English).
Chang C Y, Chang S J, Liu C H, et al. GaN-based LEDs with an HT-AlN nucleation layer prepared on patterned sapphire substrate [J]. IEEE Photon. Tech. Lett., 2013, 25(1):88-90.
Gutt R, Passow T, Pletschen W, et al. Efficient 350 nm LEDs on low edge threading dislocation density AlGaN buffer layers [J]. SPIE, 2011, 7954:79540Q-1-8.
Iida D, Sowa M, Kondo Y, et al. In situ X-ray diffraction monitoring during metalorganic vapor phase epitaxy growth of low-temperature-GaN buffer layer [J]. J. Cryst. Growth, 2012, 361:1-4.
Lu M, Fang H, Li Z, et al. Multi-buffer layers effect on characteristic of GaN grown by MOCVD [J]. Chin. J. Semicond.(半导体学报), 2004, 25(5):526-529 (in Chinese).
Shin H Y, Kwon S K, Chang Y I, et al. Reducing dislocation density in GaN films using a cone-shaped patterned sapphire substrate [J]. J. Cryst. Growth, 2009, 311(17):4167-4170.
Li Y, You S, Zhu M, et al. Defect-reduced green GaInN/GaN light-emitting diode on nanopatterned sapphire [J]. Appl. Phys. Lett., 2011, 98(15):151102-1-3.
Cheng Y, Wang L, Zhang Y, et al. GaN-based light emitting diodes with hybrid micro-nano patterned sapphire substrate [J]. ECS Solid State Lett., 2013, 2(11):Q93-Q97.
Long H, Wei Y, Yu T, et al. High quality GaN epilayers grown on carbon nanotube patterned sapphire substrate by metal-organic vapor phase epitaxy [J]. CrystEngComm, 2012, 14:4728-4731.
Wang M. Effects of Substrate Pretreatments on The Quality of Gallium Nitride Epilayers . Tianjin: Hebei University of Technology, 2010 (in Chinese).
Lee J H, Lee D Y, Oh B W, et al. Comparison of InGaN-based LEDs grown on conventional sapphire and cone-shape-patterned sapphire substrate [J]. IEEE Trans. Electron. Dev., 2010, 57(1):157-163.
Zhang Y, Xing Z, Ma Z, et al. Threading dislocation density comparison between GaN grown on the patterned and conventional sapphire substrate by high resolution X-ray diffraction [J]. Sci. China: Phys., Mechan. Astron.(中国科学:物理学 力学 天文学), 2010, 53(3):465-468 (in English).
Kang D H, Song J C, Shim B Y, et al. Characteristic comparison of GaN grown on patterned sapphire substrates following growth time [J]. Jpn. J Appl. Phys., 2007, 46(4B):2563-2566.
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