Effects of the Surface Treatment on P-type GaN and a Novel Fabrication of Phosphor-free Mix-color LEDs

• Main Authors: Yu-ming Gong, 龔鈺茗
• Other Authors: Shih-chang Sheu
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/77752355807056308408

碩士 === 國立臺南大學 === 光電工程研究所 === 98 === In this study, a reduction of Ni/Au ohmic contact resistivity on p-GaN was obtained by surface treatment using N2 plasma. It has been shown that an improvement of contact resistivity can be achieved through a proper using of N2 plasma pre-treatment. The current spreading becomes better and the leakage current was absolutely decreased therefore the light output power was significantly increased. On the other hand, we have investigated the recovery of induced-damage on p-GaN during ICP etching process. It was found that the addition of N2 to Cl2 plasma in the etching of p-GaN has more positive effects. This is attributed to the preferential loss of N2 was prevented which would otherwise compensate the surface region. Furthermore, it has been found that an ohmic contact to p-GaN could be formed in a 500W, Cl2:10sccm/N2:20sccm plasma. This is a significantly improvement for applications of surface texturing on p-GaN to enhance light extraction and reduce the induced-damage during ICP etching process at the mean time. Furthermore, we have investigated the effects of N2 plasma post-treatment after ICP etching process. It was found that, in contrast, the addition of N2 to Cl2 plasma in the etching of p-GaN is more effective than the use of N2 plasma as a post-treatment for damage recovery. In this study, we also demonstrate a GaN-based phosphor-free mix-color light-emitting diode with wavelength tunable on single chip. The novel mix-color LED device was realized by the selective area growth method with blue and green MQWs grown on common n-GaN. Especially when such two LEDs were connected with metal wire in parallel electrically, the device could be operated by injection current without any phosphor-converted solution to obtain the proper ratio of blue to green EL spectrum. It has been shown that phosphor-free white light emitting diode should be predicable and realizable through the observation of trace variation of chromatic coordinates.