We uncover the origin of blue luminescence (BL) peak in Mg doped GaN thin film using a combination of experimental X-ray absorption near edge spectroscopy (XANES), first-principles calculations based on density functional theory and full multiple scattering theoretical analysis of various possible defect complexes and their XANES signatures. We demonstrate that a defect complex composed of Mg substituted at Ga site (MgGa) and Mg at interstitial site (Mgi) is primarily responsible for the observed BL by Donor-Acceptor Pair transition (DAP) associated with a deep donor state in the gap. It correlates with a higher (lower) oxidation state of N (Ga) in heavily Mg doped GaN than in its pristine structure, evident in our experiments as well as calculations. Physical and chemical mechanisms identified here point out a route to achieving efficient p-type GaN.
@article{arxiv.1708.04036,
title = {On the origin of Blue Luminescence in Mg doped GaN},
author = {Sanjay Nayak and Mukul Gupta and Umesh V. Waghmare and S. M. Shivaprasad},
journal= {arXiv preprint arXiv:1708.04036},
year = {2019}
}