Enhancement of the Performance of AlGaInP & GaN Light-Emitting Diodes

• Main Authors: Chi-Ting Wu, 吳騏廷
• Other Authors: YewChung Sermon Wu
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/50041851710649486160

碩士 === 國立交通大學 === 材料科學與工程系所 === 95 === In this thesis, the AlGaInP epi layer was transferred successfully from GaAs to SiC substrate by wafer bonding technology at first. Then the light-extraction efficiency was also increased by surface roughening and new metal reflector. The results of the experiments showed that the saturation current of SiC-light emitting diodes (LEDs) was increased. Therefore, the issue of joule-heat effect was solved by using SiC substrates instead of GaAs substrates, because of the better heat conduction SiC substrates have. The improvement of the light-extraction efficiency was due to the surface roughening and new metal reflector. As the light driven by multi-quantum well passed through the boundary of air and LEDs, the rougher surface can decreased the probability of the total reflection. Therefore, the light-extraction efficiency was improved. Because of the high reflectivity, the Ag metal was chosen to replace the BeAu alloy for reflector in the next experiments. The results of experiments also showed that the light intensity of LEDs was enhanced by using Ag reflector. The light intensity of SiC-LEDs withAg reflector and surface roughening was 4 times than that of general GaAs-LEDs at the injection current of 20mA. However, there are still some issues for using Ag reflector. The advance analyses showed that heating process might cause the agglomeration of Ag reflector and the diffusion of indium atoms. These phenomenons decreased the reflectivity of the Ag reflector. Therefore, the diffusion barrier layer (Ti/Pt/Au) and Ni thin film were used in the structure of LEDs to solve these issues. Finally, the reflectivity of the Ag reflector was enhanced as high as ~90% by means of the new scheme, even after annealing at 270℃ for 1 hour.