Defect-Related Donors, Acceptors, and Traps in GaN

Abstract

Point defects have been created in GaN by various types of irradiation: electrons (1 and 2.5 MeV, and the spectrum from 90Sr); protons (0.15 MeV, 2 MeV, and 24 GeV); He ions (5.4 MeV); γ-rays (60Co); and sputtering and e-beam deposition of metals. They have been studied by temperature-dependent Hall-effect measurements (T-Hall), deep-level transient spectroscopy (DLTS), optically detected magnetic resonance (ODMR), positron annihilation spectroscopy (PAS), and photoluminescence (PL). Confirmed defect energies, and firm or tentative defect assignments, are as follows: T-Hall (donor at 0.06 eV, VN); DLTS (electron trap at 0.18 eV (thermal 0.06 eV), VN; electron trap at 0.9 eV, NI or GaI–X); ODMR (GaI and GaI–X); PAS (VGa); PL (0.85 eV band with 0.88 eV zero-phonon line, ON or ON–GaI; 0.93 eV band; 3.37 eV line; 3.39 eV line). Many of these defect signatures have also been observed in as-grown GaN. Dislocations, of the threading-edge type, are found to be acceptor-like in n-type GaN.