First-principles identification of defect levels in Er-doped GaN

TL;DR

This study uses first-principles calculations to identify and analyze defect levels in Er-doped GaN, revealing new defect complexes and their roles in optical properties relevant for optoelectronic applications.

Contribution

It reports the first identification of specific Er-related defect complexes and their electronic levels in GaN using hybrid density functional calculations.

Findings

Identified Er-C-N-N vacancy complex with defect level at 0.18 eV below conduction band.

Discovered Er-O-N-N vacancy complex with defect level at 0.46 eV below conduction band.

Confirmed Er-N vacancy complex with a donor level at 0.61 eV, explaining experimental observations.

Abstract

Erbium (Er) doped GaN has been studied extensively for optoelectronic applications, yet its defect physics is still not well understood. In this work, we report a first-principles hybrid density functional study of the structure, energetics, and thermodynamic transition levels of Er-related defect complexes in GaN. We discover for the first time that Er$_{\rm Ga}$-C$_{\rm N}$-$V_{\rm N}$, a defect complex of Er, a C impurity, and an N vacancy, and Er$_{\rm Ga}$-O$_{\rm N}$-$V_{\rm N}$, a complex of Er, an O impurity, and an N vacancy, form defect levels at 0.18 and 0.46 eV below the conduction band, respectively. Together with Er$_{\rm Ga}$-$V_{\rm N}$, a defect complex of Er and an N vacancy which has recently been found to produce a donor level at 0.61 eV, these defect complexes provide explanation for the Er-related defect levels observed in experiments. The role of these defects in optical excitation of the luminescent Er center is also discussed.