Ab initio study of N-doped β-Ga2O3 with intrinsic defects: the structural, electronic and optical properties

We investigated the compensation mechanism between N acceptors and native defects in β-Ga2O3 by employing the approach of pseudopotential plane-wave under the density functional theory framework. Four types of defect complexes: NGa2O3VO (N-doped β-Ga2O3 with O vacancy), NGa2O3VGa (N-doped β-Ga2O3 with Ga vacancy), NGa2O3Gai (N-doped β-Ga2O3 with Ga interstitial), and NGa2O3Oi (N-doped β-Ga2O3 with O interstitial) are take into consideration. The electronic structures, formation energies, structural, and optical properties of the defect complexes are calculated. The calculated results indicate that N dopant acts as a deep acceptor with an acceptor level at 1.33 eV above the valence band maximum, which cannot be an effective P-type dopant. The formation energies of defect complexes NGa2O3VO and NGa2O3Gai under Ga-rich atmosphere condition are 2.06 eV and 2.07 eV, respectively, which are close to the value of NGa2O3 (1.90 eV) and indicate these two defect complexes are stable under Ga-rich atmosphere. Compensated by these two native defects, N-doped β-Ga2O3 converts into weak n-type conductivity. After N-doped, a slight red-shift appears in the intrinsic absorption edge. When the intrinsic defects introduced, all the other defect complexes models induce a red-shift of the optical absorption edge compared with the pure β-Ga2O3 except for NGa2O3Gai.