Time delay in InGaN multiple quantum well laser diodes at room temperature * Ji Lian(季 莲) a) † , Jiang De-Sheng(江德生) a) , Zhang Shu-Ming(张书明) a) , Liu Zong-Shun(刘宗顺) a) , Zeng Chang(曾 畅) a) , Zhao De-Gang(赵德刚) a) , Zhu Jian-Jun(朱建军) a) , Wang Hui(王 辉) a) , Duan Li-Hong(段俐宏) a) , and Yang Hui(杨 辉) b)

We have investigated the effect of AlGaN layer parameter on the ultraviolet response of n+-GaN/i-AlxGa1－xN/n+-GaN structure ultraviolet-infrared photodetector and its physical mechanism. Through the simulation, it is found that the decrease of AlGaN background concentration has a positive effect on device’s ultraviolet quantum efficiency. When AlGaN layer background concentration cannot be reduced, the decrease of its thickness can ensure the efficiency. Besides, interfical state should be minimized during materials growth and device fabrication. In addition, small reverse bias voltage can greatly increase ultraviolet quantum efficiency. All these phenomena may be mainly attributed to the existence of the back-to-back heterojunction and the opposite electrical field. It is suggested that we need to adjust structural parameters to obtain high quantum efficiency according to the materials quality in device design.

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GaN-based LED wafers with nano-folding InGaN/GaN multiple quantum wells (MQWs) are grown on n-GaN nanopillar array templates which are fabricated using self assembled Ni nanodots as etching mask. Photoluminescence (PL) spectra of the wafer show uniform light emission wavelength over the whole area of it. No blue shift of the main peak is observed in the electroluminescence (EL) spectra of the LED devices fabricated with the wafer as the injection current increases from 10 mA to 80 mA. This can be ascribed to the reduced quantum confinement Stark effect (QCSE) and the resulting less band gap tilted by strain relaxation in the nano-folded MQWs. The device shows an excellent rectifying behavior with a forward voltage of 4.6 V under 20 mA injection current.

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