通过诱导载流子的V坑传输提升GaN基绿光LED的空穴注入效率

Enhanced Hole Injection of GaN Based Green LEDs by Inducing Carrier Transport Through V-pits

为了提升GaN基多量子阱LED的空穴注入效率,设计了具有不同最后势垒层结构的GaN基多量子阱外延结构,并将其制备为绿光mini-LED发光芯片,利用低温电致发光光谱、电流电压特性测试对其载流子传输机制进行了研究。结果表明,在采用AlGaN或GaN/AlN最后势垒层的样品中,有更多载流子可以传输到深层量子阱,空穴注入效率获得提升。本文对这一现象中的载流子运输机制以及V坑缺陷在其中所起的作用进行了研究,发现这种提升主要来自空穴V坑注入比例的增大。实验还发现,过大的V坑注入比例也会造成非辐射复合率上升,从而抑制了AlGaN最后势垒层样品的电光转换效率。

In order to improve the hole injection efficiency of GaN based multiple quantum wells LED by utilizing V-pits,mini-LEDs with different structures of last quantum barrier(LQB)layer were fabricated.The LQB structures of the four samples are GaN(10 nm),AlN(10 nm),Al0.14Ga0.86N(10 nm),and GaN(8.6 nm)/AlN(1.4 nm),respectively.The recombination mechanisms were studied in these samples with low-temperature electroluminescence spectra,and further validations were carried out through current voltage characteristics testing.The results indicate that a larger proportion of holes transported to deeper quantum wells in samples with AlGaN or GaN/AlN LQB.Experimental results show that the main reason of this improvement is the increasing proportion of holes injected through sidewall quantum wells of V-pits due to the suppression of hole injection through the c-plane MQWs,thereby enhancing hole injection efficiency.LEDs with GaN/AlN LQB exhibit lower forward voltage and higher luminous efficiency.On the other hand,a larger V-pits transport ratio can increase the non-radiative recombination rate,whereas limits the efficiency of samples with AlGaN LQB.We conducted a detailed study on the carrier transport mechanisms and the roles of V-pits in GaN based LED devices.