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 heterostructures offer a promising pathway for advancing p-channel transistors. This work investigates the impact of p-GaN thickness on hole distribution and transport through temperature-dependent Hall measurements and TCAD simulations. It is demonstrated that the p-channel is composed of holes both in the p-GaN layer and in the 2DHG at the GaN/AlGaN heterointerface at 300 K, whereas at 77 K, the p-channel conduction is dominated solely by the 2DHG at the GaN/AlGaN heterointerface. The results also reveal the formation of a polarization-induced 2DHG at the GaN/AlGaN interface, exhibiting a high sheet density of 2.2 × 10¹³ cm⁻² and a mobility of 16.2 cm²·V⁻¹·s⁻¹ at 300 K. The 2DHG sheet density remains nearly independent of p-GaN thickness when the p-GaN layer exceeds 30 nm. 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 under the influence of surface trap states.