Theoretical studies of the bipolar properties of ScAlN/AlGaN/GaN heterostructures for enhanced device applications

Abstract Here, we describe a systematic theoretical study of ScAlN/AlGaN/GaN heterostructures for enhanced high-electron-mobility transistors (HEMTs). We have investigated the carrier distributions and energy-band diagrams by solving the coupled Schrödinger and Poisson equations self-consistently. When the heterostructure is in the “off” state, the two-dimensional electron gas (2DEG) becomes increasingly depleted as the ScAlN thickness is increased to the critical thickness, at which point the two-dimensional hole gas (2DHG) appears. This critical thickness depends on the Sc content. Increasing the AlGaN thickness or Al content causes a simultaneous increase in the 2DEG and 2DHG sheet densities. In addition, when the HEMT is in the “on” state, 2DEG sheet density increases as ScAlN thickness increases, so long as the Sc content is less than 0.3; when the Sc content exceeds 0.4, this trend is reversed. For a given Sc content, double channels are produced when the ScAlN thickness exceeds the critical thickness.