Hole traps related to nitrogen displacement in p-type GaN grown by metalorganic vapor phase epitaxy on freestanding GaN

Abstract

This work investigated deep levels in p-type GaN originating from intrinsic point defects, using deep level transient spectroscopy (DLTS) to examine homoepitaxial GaN p+–p−–n+ junction diodes grown via metalorganic vapor-phase epitaxy. Following exposure to an electron beam with an energy of 137 keV that generated nitrogen vacancies (VN) and nitrogen interstitials (NI), a peak due to EHa hole traps (at 0.52 eV) was observed in DLTS spectra. The injection of minority carriers resulting from applying a forward bias generated signals for EHb (0.5 eV) and EHc (0.8 eV) hole traps while decreasing the EHa signal and increasing the net accepter concentration. The generation of EHa traps can likely be attributed to VN (3+/+) or NI (2+/+) defects based on the results of first-principles calculations. The EHb and EHc hole traps may have been associated with complex defects, including those that generated EHa traps, because these two traps appeared as the concentration of EHa traps decreased.