Exploring the feasibility and conduction mechanisms of P-type nitrogen-doped beta-Ga2O3 with high hole mobility

P-type doping of ultrawide-bandgap semiconductors, which are the key materials for fabrication of next-generation high-performance optoelectronic and electronic devices, is extremely difficult to achieve. The lack of p-type Ga2O3 has become a great obstacle to fabricate a full Ga2O3-based p-n homojunction for high-performance device applications. We demonstrate that N-doped beta-Ga2O3 achieved by a phase transition from GaN to beta-Ga2O3 possesses low formation energy and transition level epsilon(0/-), thereby with good N dopant solubility and low activation energy of N acceptors (0.355 eV). The delocalization effect, enhancement of valence band dispersion, and thus the decrease of the hole effective mass are predicted for N-doped beta-Ga2O3 due to the hybridization of O 2p with N 2p and Ga 4s orbitals. Activated hole concentrations of 6.1 x 10(15) and 2.1 x 10(16) cm(-3) at a valence band maximum are predicted for beta-Ga2O3:N-O(III) obtained by the nonspin and spin-polarized calculations, respectively. The hole mobility is 1.3 cm(2) V-1 s(-1) for undoped beta-Ga2O3 and remarkably increases to 8.8 and 5.5 cm(2) V-1 s(-1) for beta-Ga2O3:N-O(III) obtained by the non-spin and spin-polarized calculations, respectively. The origins for the unusual increase of hole mobility are attributed to the decrease of the hole effective mass, and reduction in acoustic deformation potential scattering and optical phonon scattering due to the weakening of electron-phonon coupling by N-induced phonon stiffening for beta-Ga2O3:N-O(III). The p-type conductivity of N-doped beta-Ga2O3 is demonstrated theoretically and also experimentally with a Hall hole concentration of 3.19 x 10(15) cm(-3) and a Hall hole mobility of 23.1 cm(2) V-1 s(-1) for N-doped beta-Ga2O3 films, and the p-type conductivity mechanisms are clarified. These studies will open a new horizon for other p-type wide bandgap oxide semiconductors.