P-type nitrogen-doped β-Ga 2 O 3 : the role of stable shallow acceptor N O -V Ga complexes.

In-depth understanding of the acceptor states and origins of p-type conductivity is essential and critical to overcome the great challenge for the p-type doping of ultrawide-bandgap oxide semiconductors. In this study we find that stable N O -V Ga complexes can be formed with ε (0/-) transition levels significantly smaller than those of the isolated N O and V Ga defects using N 2 as the dopant source. Due to the defect-induced crystal-field splitting of the p orbitals of Ga, O and N atoms, and the Coulomb binding between N O(II) and V Ga(I) , an a ' doublet state at 1.43 eV and an a '' singlet state at 0.22 eV above the valence band maximum (VBM) are formed for the β-Ga 2 O 3 :N O(II) -V Ga(I) complexes with an activated hole concentration of 8.5 × 10 17 cm -3 at the VBM, indicating the formation of a shallow acceptor level and the feasibility to obtain p-type conductivity in β-Ga 2 O 3 even when using N 2 as the dopant source. Considering the transition from N O(II) -V0Ga(I) + e to N O(II) -V-Ga(I), an emission peak at 385 nm with a Franck-Condon shift of 1.08 eV is predicted. These findings are of general scientific significance as well as technological application significance for p-type doping of ultrawide-bandgap oxide semiconductors.