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
English Abstract
Effect of plasma surface treatment on embedded n-contact for GaN-based blue light-emitting diodes grown on Si substrate
Feng Bo1,2,Deng Biao2,
Liu Le-Gong2,
Li Zeng-Cheng2,
Feng Mei-Xin3,
Zhao Han-Min2,
Sun Qian2,3
1.National Institute of LED on Silicon Substrate, Nanchang University, Nanchang 330047, China;
2.Lattice Power (Jiangxi) Corporation, Nanchang 330029, China;
3.Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
Fund Project: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).Received Date:13 October 2016
Accepted Date:21 November 2016
Published Online:05 February 2017
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 mm1.1 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.
Keywords: GaN/
light-emitting diode/
plasma surface treatment/
n-contact
