GaN Heterostructure With InAlGaN/AlGaN Composite Barrier Layer

GaN-based semiconductor high electron mobility transistor HEMT devices have an unparalleled advantage, particularly exhibit a very high power density, high efficiency, wide energy gap and so on. Among all the GaN-based HEMT devices, AlGaN/GaN structure is the most representative heterojunction, and the structure capable of forming high density and high mobility two-dimensional electron gas, which is the key to the superior characteristics. In order to further improve the properties of GaN-based heterostructures, In Al N /GaN and InAlGaN/GaN heterostructure attracted huge attentions in recent years, because of the higher density of two-dimensional electron gas than that of AlGaN/GaN heterostructures. However, due to the In atoms is easy to form the cluster, resulting in the two-dimensional electron gas mobility in the both In-contained GaN-based heterostructures has been limited, which significantly less than the AlGaN/GaN heterostructures.To combine the advantage of AlGaN/GaN and InAlGaN/GaN heterostructures, this paper focus on the research on GaN-based heterostructures with InAlGaN/AlGaN composite barrier layer. and the main work are as follows:1. PMOCVD growth method have been used instead of the conventional MOCVD growth method, and the study have found that InAlGaN/GaN heterostructures grown by PMOCVD get better crystal quality and surface morphology.2. The Heterojunction structure with InAlGaN/AlGaN/GaN composite barrier layer was successfully grown, by compare with the AlGaN/GaN and InAlGaN/GaN heterostructures, It is found that InAlGaN/AlGaN/GaN heterostructures have better two-dimensional electron gas properties.3. The formation mechanism of the circular dislocation pit on the surface of InAlGaN/AlGaN/GaN have been found and studied.and its influence on the PL spectrum of the materials have been analysised4. The influence of different thickness of AlGaN layer on the optical and electrical properties of InAlGaN/AlGaN/GaN is studied. It is found that the InAlGaN barrier layer can adaptively adjust its components adaptively and lead to the tensile strain reducing as the thickness of the AlGaN layer increases. The experimental results also show that the thickness of AlGaN layer and the Al component of InAlGaN layer can significantly affect the density and electron mobility of two dimensional electron gas. The analysis shows that the change of the mobility is mainly affected by the disorder of the alloy.