The characteristics and polarization effects in AlInGaN barrier GaN MISHEMT with various compositions of group III elements.

This study investigates the impact of varying compositions of Al_xIn_yGa_zN barrier layers on the performance of Al_xIn_yGa_zN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors (MISHEMTs) using Sentaurus TCAD simulation. By systematically increasing the compositions of Al and In and decreasing the Ga composition of the Al_xIn_yGa_zN layer, we maintained the lattice-matched conditions with GaN and explored the effects of compositions on channel charge, drain current, and threshold voltages. Under the lattice-matching conditions, it was shown that the Al_xIn_yGa_zN barrier with higher Al/In and lower Ga exhibited significantly enhanced channel charges and drain current while making threshold voltages more negative. Additionally, the influence of Al_xIn_yGa_zN layer thickness was studied. Subsequently, we analyzed the electrical characteristics of Al_xIn_yGa_zN/GaN MISHEMT based on systematically changing the compositions of each group III element. The lattice mismatch-related piezoelectric polarization was also taken into consideration. Our results indicate that total polarization increases as Al composition increases; however, the total polarization decreases as In composition increases. Notably, the change in total polarization looked slightly stronger by varying In composition compared to Al. Furthermore, we compared the charge density and band structures of MISHEMT heterostructures with and without the AlN spacer layer. The inclusion of an AlN spacer layer was found to enhance carrier confinement and reduce the dependence of charge density on composition due to the presence of large polarization between the barrier layer and channel layer. These findings highlight the importance of precise material composition control in optimizing MISHEMT performance.