Effect of Hydrogen Treatment on Photoluminescence and Morphology of InGaN Multiple Quantum Wells

Abstract

In this paper, the photoluminescence (PL) properties and surface morphology of InGaN/GaN multiple quantum well (MQW) structures with the hydrogen (H2) heat treatment of InGaN are investigated to elucidate the effect of hydrogen on the structure and surface of the MQWs. The experimental results show that the H2 heat treatment on the as-grown MQWs may lead to the decomposition of InGaN and the formation of inhomogeneous In clusters. The atomic force microscope (AFM) study indicates that although the surface roughness of the uncapped samples increases after H2 treatment, the V-defects are suppressed. Moreover, the luminescence efficiency of the MQWs can be effectively improved by growing a GaN cap layer with an appropriate thickness on the top of the MQWs, which can reduce the effects of the H2 atmosphere and high temperature on the MQWs. In addition, a morphologic transformation from step bunching to shallow steps occurs and a much smoother surface can be obtained when a thicker cap layer is adopted.

Fabrication of High Efficiency Green InGaN/GaN MicroLEDs by Modulating Potential Barrier Height of the Sidewall MQWs in V-Pits

“…As the hydrogen flow rate increases, the enhanced diffusion of Ga atoms plays a dominant role, which is beneficial in enhancing the 2dimensional growth and suppresses the formation of new pits especially for small pits that begin to grow in last few quantum wells but has little effect on large V-pits that have already formed before MQWs [19], [20]. Moreover, the hydrogen remove the In-rich clusters from the MQWs, therefor reducing stress accumulation may also played a significant role [12]. According to the Table I, the density and size of large V-pits of two samples are almost the same, but the absence of small V-pits in sample 2 is the major difference and their impact and effect on the MicroLEDs performance will be revealed in below discussion.…”

“…R. Czernecki, et al reported that the H2 flow reduced the indium concentration and thickness of the QWs and increase the thickness of the barriers [11]. However, Wu et al reported that the MQWs under H2 treatment has a lower EQE, while the forward and reverse currents will be reduced [12]. Such different results reported may be due to the different H2 flow rate in the carrier gas or different growth processes of the QWs.…”