Probing the effects of surface roughness and barrier layer thickness in InAlGaN/GaN HEMTs to improve carrier mobility

In this study, we investigated the effects of the thickness and surface roughness of InAlGaN barrier layers on the electron mobility of InAlGaN/GaN high-electron-mobility transistors (HEMTs) with low sheet resistance for applications at high frequencies. The results indicate that the carrier electron mobility of InAlGaN/GaN HEMTs decreases with barrier thickness. This is mainly due to the surface roughness of the InAlGaN barrier layer, which is significantly higher than that of the AlGaN barrier surface. In our experiments, we revealed that a thin GaN cap layer led to a decrease in the surface roughness of the InAlGaN barrier layer, thereby improving the electron mobility.