Distribution and transport of holes in the p-GaN/AlGaN/GaN heterostructure

Abstract

The p-GaN/AlGaN/GaN heterostructure, predominantly epitaxially grown on large-scale silicon wafers, has been widely used for producing consumer power switching devices and recently manifested favorable for developing GaN-based complementary devices and circuits. This work investigates the hole distribution and transport in this structure based on wide-temperature-range (20–600 K) Hall measurements and TCAD simulations. It is revealed that the p-channel thereof is composed of the bulk holes in the p-GaN and the two-dimensional hole gas (2DHG) at the p-GaN/AlGaN interface, and both substantially contribute to the lateral p-type conduction at room temperature. Their complementary temperature responses lead to conductivity enhancement at both high- and low-temperature regimes. The high-density (1.2 × 1013 cm−2) 2DHG is formed owing to the polarization-induced potential well and the ionization of the Mg acceptors that thermally diffused into the barrier during the epi-growth. Such ionized Mg acceptors would partially deplete the two-dimensional electron gas (2DEG) at the access region in the n-channel side where the p-GaN is removed and result in a trade-off between the carrier density of 2DHG and 2DEG.