Impact of p-GaN thickness on the transport properties of two-dimensional hole gases in a GaN/AlGaN/GaN heterostructure

Polarization-induced two-dimensional hole gases (2DHG) in GaN/AlGaN/GaN heterostructure offer a promising pathway for advancing p-channel transistors. This work investigates the impact of p-GaN thickness on the hole distribution and transport by temperature-dependent Hall measurements and TCAD simulations. It is demonstrated that the p-channel is composed of holes in both the p-GaN layer and the 2DHG at the GaN/AlGaN heterointerface at 300 K, but the p-channel is contributed by the 2DHG at the GaN/AlGaN heterointerface only at 77 K. The results also reveal that the formation of a polarization-induced 2DHG at the GaN/AlGaN interface, exhibiting a high sheet density of 2.2×10 13 cm -2 and mobility of 16.2 cm 2 /V·s at 300 K. The 2DHG sheet density remains independent of p-GaN thickness when the p-GaN layer exceeds 30nm. However, for p-GaN layers thinner than 30 nm, the 2DHG sheet density strongly depends on the p-GaN thickness, which is attributed to the gradual extension of the depletion region toward the GaN/AlGaN interface due to the influence of the surface trap states.