Optical properties of irradiated epitaxial GaN films

TL;DR

This study investigates how microwave treatment affects the optical properties and structural perfection of irradiated GaN films, revealing strain relaxation and improved surface quality through electroreflectance measurements.

Contribution

It introduces a mechanism involving resonance effects and local heating to explain the observed improvements in GaN films after microwave irradiation.

Findings

Microwave treatment relaxes internal mechanical strains.

Structural perfection in the near-surface layer increases.

Resonance effects and local heating explain the observed phenomena.

Abstract

The influence of a microwave treatment (MWT) on the optical properties of hexagonal GaN films has been studied. To estimate the internal mechanical strains and the degree of structural perfection in a thin near-surface layer of the film, the electroreflectance (ER) method is used. The ER spectra are measured in the interval of the first direct interband transitions. It has been shown that the MWT results in the relaxation of internal mechanical strains in the irradiated films. In addition, the structural perfection in the thin near-surface layer of the irradiated film became higher. A mechanism that includes resonance effects and the local heating of the film defect regions is proposed to explain the effects observed.