Impacts of hydrogen flow and growth pressure on characteristics of semipolar (11 [formula omitted] 2) plane AlInGaN quaternary epilayers

Abstract

The semipolar (11 2‾ 2) plane AlInGaN quaternary epilayer was successfully grown by metal-organic chemical vapor deposition (MOCVD) technology. The impacts of hydrogen flow and growth pressure on indium incorporation, growth rate, surface morphology, and crystalline quality of the semipolar AlInGaN epilayers were investigated extensively. It was found that the indium incorporation, growth rate, surface morphology, and crystalline quality of the semipolar AlInGaN epilayers were strongly dependent on the constituent of reaction gas and growth pressure in MOCVD growth process. In fact, an evident decrease in the number of hillock-like features and a slight increase in the size of hillock-like features were observed on the surfaces of the semipolar AlInGaN epilayers as the proportion of hydrogen in reaction gas was gradually increased. A root mean square value as small as 2.7 nm and an indium composition of 3.2% were achieved by adding extra 15% hydrogen in reaction gas. On the other hand, an enhanced indium composition of 3.9% was obtained together with a 64% reduction in growth rate and dramatic degradation in surface morphology and crystalline quality by increasing the growth pressure from 40 to 100 Torr for the semipolar AlInGaN epilayer due to aggravated parasitic reactions. This fact indicates that the conventional method, namely simply increasing growth pressure is not a good option to obtain high indium composition in the semipolar AlInGaN quaternary alloy.