Band alignment and charge carrier transport properties of YAlN/III-nitride heterostructures

Abstract

Incorporating rare earth element scandium (Sc) into III-nitride wurtzite lattice offers remarkable non-oxide ferroelectrics, tunable spontaneous polarization coefficients, and significantly enhanced linear and nonlinear optical properties. Yttrium (Y), a Sc substitute, is also capable of similar properties when alloyed with III-nitride materials, but its potential has remained largely unexplored. In this study, we present the first experimental investigation into the energy band gap alignment and transport properties of a YAlN based high-electron-mobility transistor (HEMT) structure. Our measurements revealed a type-I band alignment for the Y0.07Al0.93N/GaN heterojunction, with a small valence band offset of −0.1 eV and conduction band offset of 2.2 eV. We then developed a novel Y0.07Al0.93N/AlN/GaN heterojunction-based HEMT and evaluated its transport properties. A mobility of 1000 cm2/Vs, a sheet electron concentration of 4.2 × 1013 cm2, and a sheet resistance of 148 Ω/□ were measured at room temperature, which are among the best values reported for rare earth element-containing nitride epitaxial heterostructures. We have further performed temperature-dependent Hall measurements and identified the dominant factors affecting transport properties at different temperature ranges. The excellent electrical characteristics and compatibility with mainstream semiconductor technology represent a significant step forward in the development of next-generation multifunctional HEMTs.