Effect of V‐pits embedded InGaN/GaN superlattices on optical and electrical properties of GaN‐based green light‐emitting diodes

Abstract

We investigated effects of V‐pits embedded InGaN/GaN superlattices (SL) on optical and electrical properties of high power green LEDs by changing the number of SL period and SL growth temperature. Surface morphology of V‐pits embedded InGaN/GaN SL with various periods and growth temperatures was evaluated by using atomic force microscopy (AFM). It was found that density and size of V‐pit increase with decreasing SL growth temperature and increasing SL periods. Experimental studies using scanning electron microscopy (SEM) equipped with cathodoluminescence (CL) indicated that SL with larger V‐pits appear to be more effective in suppressing the lateral diffusion of carriers into threading dislocations (TD). Compared to c‐plane quantum wells, narrower quantum wells on the V‐pit sidewall were clearly observed by performing high‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM). The external quantum efficiency (EQE) and the efficiency droop of green LEDs grown on underlying SL with larger V‐pits are improved at high injection current regime, which is attributed to a more efficient hole injection into multiple quantum well, and also to a higher V‐pit potential barrier height that could more effectively suppress the lateral diffusion of carriers into non‐radiative recombination centers of TDs.