Light extraction efficiency enhancement of GaN-based light emitting diodes by a ZnO current spreading layer

• Published in: Journal of semiconductors Vol. 30; no. 9; pp. 29 - 32
• Main Author: 杨华 王晓峰 阮军 李志聪 伊晓燕 段垚 曾一平 王国宏
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.09.2009
• Subjects: 光提取效率; 发光二极管; 基础; 扩散层; 氧化锌薄膜; 氮化镓薄膜; 电流; 铟锡氧化物
• ISSN: 1674-4926
• DOI: 10.1088/1674-4926/30/9/094002

Gallium nitride （GaN） based light emitting diodes （LEDs） with a thick and high quality ZnO film as a current spreading layer grown by metal-source vapor phase epitaxy （MVPE） are fabricated successfully. Compared with GaN-based LEDs employing a Ni/Au or an indium tin oxide transparent current spreading layer, these LEDs show an enhancement of the external quantum efficiency of 93% and 35% at a forward current of 20 mA, respectively. The full width at half maximum of the ZnO （002） ω-scan rocking curve is 93 arcsec, which corresponds to a high crystal quality of the ZnO film. Optical microscopy and atomic force microscopy are used to observe the surface morphology of the ZnO film, and many regular hexagonal features are found. A spectrophotometer is used to study the different absorption properties between the ZnO film and the indium tin oxide film of the GaN LED. The mechanisms of the extraction quantum efficiency increase and the series resistance change of the GaN-based LEDs with ZnO transparent current spreading layers are analyzed.