The Study of Highly Efficiency Nitride based LEDs

• Main Authors: Hsin-Ming Lo, 羅信明
• Other Authors: Shoou-Jinn Chang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/17926711814835830010

碩士 === 國立成功大學 === 電機工程學系碩博士班 === 95 === In this dissertation, the nitride based epitaxy material was grown by metalorganic chemical vapor deposition (MOCVD). We have succeeded in fabricating highly efficient nitride based light emitting diodes with high electrostatic discharge (ESD) ability. For increasing the output efficiency of the LED devices, highly transparent Indium-tin-oxide films were used to be the transparent contact layer. In order to increasing spreading path of the electron-hole pairs, ICP dry etching was used to separate the current spreading path. It was found that 6 % output power could be enhanced with ICP dry etching technique. In the same theory, the insulation layer was deposition under the p-pad electrode as the current blocking layer. The 20 mA output power of the LEDs with insulation layer and without insulation layer was 3.65 mA and 3.32 mW, respectively. 7~10 % enhancement of the output intensity could be obtained. In the other way, nano-roughness of n-type GaN epitaxy layers were also applied on the LED devices. It was found that different density of the nano-roughness could be obtained with the different dry etching rate that was due to the different reaction gas. The 20 mA output power was 26.74 lm/W for the LED with nano-roughness and 25.44 lm/W for the LED without nano-roughness. The output intensity was increased about 12 %. For the improvement of electrostatic discharge, due to the characteristics of the PN junction diode, the forward ESD ability of the LED could be more than 3000 V, however, the LED device was damaged easily by the was less than 300V that reverse electrostatic discharge. In order to avoid the damage of LED from the electrostatic discharge during operation, the LED and an ESD diode are connected in parallel and in reverse. Moreover, flip-chip process was also applied on the LED fabrication for increasing the output brightness. It was found that the electrostatic discharge capability of the flip-chip LED with ESD protection could be greatly improved from 300 V to 1200 V in human body model (HBM). Furthermore, 70 % increase of the output power was also achieved by the flip-chip technique.