Effects of Surface Roughening by Epitaxical Growth on Light Emitting Diodes for High Brightness Applications

• Main Authors: Tsung-Liang Chen, 陳宗良
• Other Authors: 洪瑞華
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/52215760564199369733

碩士 === 國立中興大學 === 精密工程學系所 === 95 === Abstract In this investigation, we studied the effect of surface roughing on light extraction efficiency. The electrical and optical properties were characterized by electroluminescence and surface morphology measured by microscope and Scanning Electron Microscope. In order to improve the light extraction efficiency, we tried to implement various growth conditions of P-type GaN layers to create surface roughing, such as pits-like and island-like surface. Experiment results indicated that the island-like surface had better light extraction efficiency. The light extraction efficiency was 84.3 % in island-like LED surface, and the light extraction efficiency increased 48 % as compared with that of non-surface roughing LEDs. But the forward driving voltage of island-like surface LED was 3.39V, and the forward driving voltage of non-surface roughing and pits-like surface LEDs were 3.28 V and 3.19 V. The forward driving voltage was higher than non-surface roughing and pits-like surface. In this investigation, we implemented various parameters on growth temperature and pressure in order to create island-like surface. Base on 1000 ℃ growth temperature for island-like surface, we implemented 900 ℃ and 1100 ℃ for P-type growth individually. The light extraction efficiency were 74.21 % and 59.08 %. Experiment result indicated that the light extraction efficiency decayed both respected to 900 ℃ or 1100 ℃. On the other hand, we changed growth pressure from 250 torr to 100 torr and 400 torr for p-type growth individually. The light extraction efficiency were 81.04 % and 87.17 %. Experiment result indicated that island-like growth pressure in 400 torr had best light extraction efficiency. The light extraction efficiency increased 3.4 % compared to island-like growth pressure in 250 torr.