材料科学
发光二极管
光电子学
电致发光
蓝宝石
光致发光
二极管
量子限制斯塔克效应
光学
基质(水族馆)
量子阱
激光器
图层(电子)
纳米技术
海洋学
物理
地质学
作者
Minyan Zhang,Yufeng Li,Qiang Li,Xilin Su,Shuai Wang,Lishuang Feng,Zhenhuan Tian,Minghui Guo,Guowei Zhang,Wen Ding,Feng Yun
摘要
GaN-based 500 nm light-emitting diodes (LEDs) with an air-cavity formed on a laser-drilled hemispherical patterned sapphire substrate (HPSS) were investigated. The cross-section transmission electron microscopy image of the HPSS-LED epilayer indicated that most of the threading dislocations were bent towards the lateral directions. It was found that in InGaN/GaN multiple quantum wells (MQWs) of HPSS-LEDs, there were fewer V-pits and lower surface roughness than those of conventional LEDs which were grown on flat sapphire substrates (FSSs). The high-resolution x-ray diffraction showed that the LED grown on a HPSS has better crystal quality than that grown on a FSS. Compared to FSS-LEDs, the photoluminescence (PL) intensity, the light output power, and the external quantum efficiency at an injected current of 20 mA for the HPSS-LED were enhanced by 81%, 65%, and 62%, respectively, such enhancements can be attributed to better GaN epitaxial quality and higher light extraction. The slightly peak wavelength blueshift of electroluminescence for the HPSS-LED indicated that the quantum confined Stark effect in the InGaN/GaN MQWs has been reduced. Furthermore, it was found that the far-field radiation patterns of the HPSS-LED have smaller view angles than that of the FSS-LED. In addition, the scanning near field optical microscope results revealed that the area above the air-cavity has a larger PL intensity than that without an air-cavity, and the closer to the middle of the air-cavity the stronger the PL intensity. These nano-light distribution findings were in good agreement with the simulation results obtained by the finite difference time domain method.
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