等离子体表面处理对硅衬底GaN基蓝光发光二极管内置n型欧姆接触的影响
Effect of plasma surface treatment on embedded n-contact for GaN-based blue light-emitting diodes grown on Si substrate
摘要
Abstract
Unlike the finger-like n-contact that is prepared after the wafer bonding and the N-polar GaN surface roughening for GaN-based vertical structure light-emitting diodes (LEDs) grown on Si substrates, the embedded via-like n-contact is formed prior to the wafer bonding. The high temperature process of the wafer bonding often causes the electrical characteristics of the via-like embedded n-contact to degrade. In this paper, we study in detail the effect of plasma treatment of the n-GaN surface on the forward voltage of GaN-based LED grown on Si substrate. It is shown that with no plasma treatment on the n-GaN surface, the forward voltage (at 350 mA) of the 1.1 mm × 1.1 mm chip with a highly reflective electrode of Cr (1.1 nm)/Al is 3.43 V, which is 0.28 V higher than that of the chip with a pure Cr-based electrode. The LED forward voltages for both kinds of n-contacts can be reduced by an O2 plasma treatment on the n-GaN surface. But the LED forward voltage with a Cr/Al-based electrode is still 0.14 V higher than that of the chips with a pure Cr-based electrode. However, after an Ar plasma treatment on the n-GaN surface, the LED forward voltage with a Cr/Al-based electrode is reduced to 2.92 V, which is equal to that of the chip with a pure Cr-based electrode. The process window of the n-GaN surface after the Ar plasma treatment is broader. X-ray photoelectron spectroscopy is used to help elucidate the mechanism. It is found that Ar plasma treatment can increase the concentration of N-vacancies (VN) at the n-GaN surface. VN acts as donors, and higher VN helps improve the thermal stability of n-contact because it alleviates the degradation of the n-contact characteristics caused by the high temperature wafer bonding process. It is also found that the O content increases slightly after the Ar plasma treatment and HCl cleaning. The O atoms are mainly present in the dielectric GaOx film before the Ar plasma treatment and the HCl cleaning, and they exist almost equivalently in the conductive GaOxN1?x film and the dielectric GaOx film after Ar treatment and HCl cleaning. The conductive GaOxN1?x film and the VN donors formed during the plasma treatment can reduce the contact resistance and the LED forward voltage.关键词
氮化镓/发光二极管/等离子体表面处理/n型欧姆接触Key words
GaN/light-emitting diode/plasma surface treatment/n-contact引用本文复制引用
封波,邓彪,刘乐功,李增成,冯美鑫,赵汉民,孙钱..等离子体表面处理对硅衬底GaN基蓝光发光二极管内置n型欧姆接触的影响[J].物理学报,2017,66(4):276-283,8.基金项目
Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA03A102), the National Key Research and Development Program of China (Grant No. 2016YFB0400104), the National Natural Science Foundation of China (Grant Nos. 61534007, 61404156, 61522407, 61604168), the Key Frontier Scientific Research Program of the Chinese Academy of Sciences (Grant No. QYZDB-SSW-JSC014), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20160401), the China Postdoctoral Science Foundation (Grant No. 2016M591944), the Open Fund of the State Key Laboratory of Luminescence and Applications, China (Grant No. SKLA-2016-01), the Open Fund of the State Key Laboratory on Integrated Optoelectronics (Grant Nos. IOSKL2016KF04, IOSKL2016KF07), and the Seed Fund from SINANO, Chinese Academy of Sciences (Grant No. Y5AAQ51001). 国家高技术研究发展计划(批准号: 2015AA03A102)、国家重点研发计划(批准号: 2016YFB0400104)、国家自然科学基金(批准号: 61534007, 61404156, 61522407, 61604168)、中国科学院前沿科学重点研究项目(批准号: QYZDB-SSW-JSC014)、江苏省自然科学基金(批准号: BK20160401)、中国博士后基金(批准号: 2016M591944)、发光学及应用国家重点实验室开放课题(批准号:SKLA-2016-01)、集成光电子学国家重点联合实验室开放课题(批准号: IOSKL2016KF04, IOSKL2016KF07)和中国科学院苏州纳米技术与纳米仿生研究所自有资金(批准号: Y5AAQ51001) 资助的课题. （Grant No. 2015AA03A102）
