Enhanced transport properties in GaN heterostructures with sputter-epitaxy-grown ScAlN barriers via thermal annealing

ScAlN has attracted considerable attention as a promising barrier material in GaN-based high-electron-mobility transistors. However, few studies have been conducted on the effect of thermal annealing on the structural, electrical, and transport properties of ScAlN barrier layer sputter-deposited on an AlGaN/AlN/GaN heterostructure. Therefore, in this study, ScAlN barrier layers were grown by sputter epitaxy on templates prepared via metalorganic vapor phase deposition. Post-deposition annealing was conducted at 750 °C, which preserved the wurtzite structure of the ScAlN films and maintained coherent interfaces without interdiffusion or phase change. Hall effect measurements revealed that annealing substantially increased the sheet carrier concentration (∼8.0×1012cm−2) and electron mobility exceeding 1000 cm2 V−1 s−1 of the heterostructure. The mobility was limited by acoustic deformation potential, polar optical phonon, and interface roughness scattering. Notably, the increased roughness scattering at higher Sc content might be due to local compositional fluctuations. These results demonstrate that thermal annealing effectively enhances the transport properties of ScAlN barrier layers sputter-deposited on GaN-based heterostructures, offering a promising route for fabricating high-performance and scalable GaN-based electronic devices.