On the origin of Blue Luminescence in Mg doped GaN

TL;DR

This study identifies the defect complex responsible for blue luminescence in Mg-doped GaN using experimental spectroscopy and theoretical calculations, revealing insights into defect states and p-type doping mechanisms.

Contribution

It combines experimental XANES and first-principles calculations to pinpoint the Mg-related defect complex causing blue luminescence in GaN, advancing understanding of defect-induced optical properties.

Findings

MgGa and Mgi defect complex causes BL via DAP transition

Higher oxidation state of N correlates with Mg doping

Provides a route for efficient p-type GaN

Abstract

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.