Energy-driven multi-step structural phase transition mechanism to achieve high-quality p-type nitrogen-doped β-Ga2O3 films

It is a big challenge to grow β-Ga2O3 films of good p-type conductivity and stability due to the large acceptor ionization energy, strong hole-trapping effect, low hole mobility, and self-compensation effects. In this study, we demonstrate for the first time the success in the growth of high-quality p-type N-doped β-Ga2O3 films with an acceptor ionization energy of 0.165 eV, Hall resistivity of 17.0 Ωcm, Hall hole mobility of 23.6 cm2V−1s−1, hole concentration of 1.56 × 1016 cm−3 and good stability, and in the fabrication of high-performance p-type β-Ga2O3 films-based field effect transistors. The success paves the way to fabricate full β-Ga2O3 films based p-n diodes and will advance the applications of next-generation high-performance β-Ga2O3-based optoelectronic and electronic devices. In addition, we discover the growth mechanism of multi-step structural phase transitions from hexagonal P63mc GaN to rhombohedral R3¯c α-GaNxO3(1-x)/2 and finally to monolithic C2/m N-doped β-Ga2O3, which improves the crystalline quality, facilitates the acceptor doping, increases the acceptor activation efficiency, and thus enhances the p-type conductivity and stability of the N-doped β-Ga2O3 films. The novel p-type oxide film growth technique and mechanism open a new horizon to the other wide bandgap oxide semiconductors.