Hybrid functional study of acceptor levels in β-Ga2O3 with stress engineering

Abstract

β-Ga2O3 has emerged as a wide-bandgap semiconductor material, which can be widely used in high-power electronic devices and solar blind ultraviolet detectors. Nevertheless, the challenge of p-type doping is a huge obstacle to the application of β-Ga2O3. Numerous studies have been devoted to finding p-type dopants for β-Ga2O3. However, the outcomes have been less than satisfactory due to its valence bands with small dispersions and self-trapped hole properties. Herein, using the hybrid functional method, 27 defect configurations are built to reveal the possibility of p-type doping, containing MgGa, NO, PO, transition metal substitutions (TMGa), and complex defects. First, unlike conventional defect calculations that employ generalized gradient approximation (GGA) or meta-GGA for structural optimization, we demonstrate that only hybrid functional can capture the large structural distortions caused by polarons in β-Ga2O3. Notably, defects previously classified as shallow-level centers (e.g., Po and MgGa–No complexes) are revealed to form deep-level states at our theoretical level of treatment. Second, for TMGa defects, only the TM atoms from VIII to IIB exhibit acceptor level. Furthermore, the strain can significantly regulate the acceptor levels of NiGa and CuGa. However, the acceptor levels of MgGa and ZnGa exhibit high tolerance to strain. Our results provide a reference for the study of p-type doping of β-Ga2O3, emphasizing the criteria of hybrid functional optimization and the difficulty in forming shallow acceptor levels using conventional substitutional defects.