Origin of blue luminescence in Mg-doped GaN

Jing Wang,Wanzhu Shu,Jiafan Chen,Xiaodan Wang,Ke Xu,Xionghui Zeng

doi:10.1063/5.0037047

Abstract

In this work, dual acceptor-bound exciton peaks are observed by low-temperature photoluminescence. The peaks correspond to the dual Mg-related acceptor levels in GaN based on the Haynes rule. By calibrating the energy-level structure, a mechanism for the origin of blue luminescence (BL) in Mg-doped GaN is proposed. The BL band is separated by thermal treatment at different temperatures, confirming the rationality of the dual-factor origin of the BL band. As the annealing temperature increases, the PL spectrum and the p-type conductivity of Mg-doped GaN also change. The experimental results indicate that there is not necessarily a relationship between the BL band and p-type conductivity in GaN grown by metalorganic chemical vapor deposition.

Highlights

Gallium nitride (GaN) is a III–V nitride semiconductor that has attracted considerable attention for its superior material properties, such as large bandgap energy (3.4 eV), high breakdown field (3.3 MV/cm), and high electron saturation velocity (∼2.5 × 107 cm s−1).1,2 GaN is an excellent candidate for lightemitting diodes, laser diodes, and high-frequency and high-power electronic devices.2 the difficulty in achieving high conductivity in p-type GaN has limited the widespread use of GaNbased devices
The incorporation of Mg in GaN results in two characteristic luminescence peaks that depend on the dopant concentration: a photoluminescence (PL) peak at 3.27 eV, which corresponds to ultraviolet luminescence (UVL),3 and a broader PL peak centered at 2.9 eV that appears at high Mg concentrations (>1019 cm−3), which corresponds to blue luminescence (BL)
The UVL has been attributed to the transition of conduction band electrons/shallow donors to the Mg acceptor lying at ∼0.18 eV above the valence band maximum (VBM)

Summary

Introduction

Gallium nitride (GaN) is a III–V nitride semiconductor that has attracted considerable attention for its superior material properties, such as large bandgap energy (3.4 eV), high breakdown field (3.3 MV/cm), and high electron saturation velocity (∼2.5 × 107 cm s−1). GaN is an excellent candidate for lightemitting diodes, laser diodes, and high-frequency and high-power electronic devices. the difficulty in achieving high conductivity in p-type GaN has limited the widespread use of GaNbased devices. GaN is an excellent candidate for lightemitting diodes, laser diodes, and high-frequency and high-power electronic devices.. The UVL has been attributed to the transition of conduction band electrons/shallow donors to the Mg acceptor lying at ∼0.18 eV above the valence band maximum (VBM).. The origin of the BL band remains unclear. Kaufmann proposed that the BL band originates from recombination between deep donors and the MgGa acceptor, a viewpoint that is widely accepted.. As for the source of the deep donors, many different explanations involving MgGa–VN, Mgi, and Mgi + MgGa have been offered.. Recent density functional theory (DFT)-based calculations suggest that the recombination of conduction band electrons to the VN+ and/or VN2+ level results in a BL band, there is no direct experimental evidence to support this explanation. As for the source of the deep donors, many different explanations involving MgGa–VN, Mgi, and Mgi + MgGa have been offered. Recent density functional theory (DFT)-based calculations suggest that the recombination of conduction band electrons to the VN+ and/or VN2+ level results in a BL band, there is no direct experimental evidence to support this explanation.

Results

Discussion

Conclusion