Investigation of Improving External Quantum Efficiency of AlGaInP-Based LEDs by Wet-Etching n-Cladding Layer

• Main Authors: Chia-Hong Wang, 王嘉宏
• Other Authors: 洪瑞華
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/23209910014023388517

碩士 === 國立中興大學 === 精密工程學系所 === 97 === High-performance AlGaInP-based light emitting diodes (LEDs) were widely used, although the AlGaInP-based material has been developed for many years and its internal quantum efficiency has approached above 90%. However, the external quantum efficiency of AlGaInP is still low due to the optical properties limitation. In this research, we use the technology of wet chemical etching to roughen the n-cladding layer AlGaInP to enhance the light extraction efficiency of light-emitting diode. It is effectively extracting the emitting light which is generated from LED’s active layer and reduced the total internal reflection. Under the 350mA injection current, the forward voltage of 1mm x 1mm LED with random roughness is about 2.1V and the emitting light is enhanced to 40%. Investigating the optical and electrical properties of AlGaInP-based LEDs, the LEDs with naturally wet chemical etching surface present 2.1V forward voltage under 350mA current injection. Moreover, it was found that the brightness can be enhanced 10% and 40%~50% as compared with those of LEDs with and without periodic texturing surface, respectively. It is worthy to mention that the texturing processes can not destroy the electrical properties of LEDs. As concerning the reliability of LEDs with surface roughness, the life test was measured under 500mA and 96hr. The variation of brightness and forward voltage is under 20%.