Room-temperature photoluminescence of Mg-doped GaN thin films grown by plasma-assisted MOCVD

Pepen Arifin,Rany Khaeroni,Donny Dwiputra,Agus Subagio,Aveni C Keintjem,Sugianto Sugianto,Fenfen F Florena,Heri Sutanto

doi:10.1063/5.0004384

Abstract

The growth of Mg-doped GaN thin films by metalorganic chemical vapor deposition (MOCVD) using NH3 and Cp2Mg as a source of nitrogen and Mg, respectively, usually produces Mg–H complexes, which hinder the activation of Mg as shallow acceptor centers. Therefore, post-growth treatments are commonly required to activate these acceptor centers. The presence of Mg dopants in GaN films induces various defect-related emissions whose characteristics depend on the growth method. For this study, we prepared Mg-doped GaN thin films by plasma-assisted MOCVD. A nitrogen-plasma, instead of NH3, served as a nitrogen source to minimize the formation of Mg–H complexes, thereby eliminating the requirement for post-growth treatment. The emission characteristics were obtained by measuring the photoluminescence of the as-grown room-temperature films. Yellow, green, blue, and ultraviolet emission bands are produced by Mg-doped samples with different Mg concentrations produced by Cp2Mg flow rates of 2%, 5%, and 10% of the total flow rate. Low-Mg concentration leads to nitrogen and gallium vacancies, which results in yellow photoluminescence. At higher Mg concentration, the yellow photoluminescence is suppressed and the blue photoluminescence is enhanced because of the incorporation of vacancies by Mg atoms. The analysis of the photoluminescence spectra leads to the proposed band diagrams for Mg-doped GaN with varying Mg concentration.

Highlights

Due to their superior optical properties, the group III-nitrides have played a major role in optoelectronic device applications, such as LEDs, laser diodes, solid-state lighting, and solar-blind ultraviolet detectors.[1,2,3,4] Remarkable progress in the development of optoelectronic devices has been made since the synthesis of p-type GaN
When the Cp2Mg flow is increased to 10%, the yellow luminescence (YL) and green luminescence (GL) bands disappear and the PL spectrum becomes dominated by a broader blue luminescence (BL) band, with a strongly diminished ultraviolet luminescence (UVL) band peaking at 3.23 eV still apparent
We report the growth of Mg-doped GaN films by plasmaassisted metalorganic chemical vapor deposition (MOCVD) with three different Cp2Mg concentrations

Summary

INTRODUCTION

Due to their superior optical properties, the group III-nitrides have played a major role in optoelectronic device applications, such as LEDs, laser diodes, solid-state lighting, and solar-blind ultraviolet detectors.[1,2,3,4] Remarkable progress in the development of optoelectronic devices has been made since the synthesis of p-type GaN Various dopants, such as Zn, Be, or Mg, have been used; Mg is the most important dopant because it leads to reproducible p-type GaN.[5] Growing Mg-doped GaN by metalorganic chemical vapor deposition (MOCVD) produces a high-resistivity material with low hole concentration that prevents it from being used for high-efficiency LEDs or laser diodes that operate at low voltage. The characteristics of the observed photoluminescence are correlated with the growth mechanism

EXPERIMENT

RESULTS AND DISCUSSION

PL max

CONCLUSION