The origin of the E+ transition in GaAsN alloys

TL;DR

This study investigates the origin of the E+ optical transition in GaAsN alloys with low nitrogen content using first-principles calculations, revealing the roles of specific electronic states and nitrogen potential effects.

Contribution

The paper identifies the electronic states responsible for the E+ transition and analyzes how nitrogen concentration and potential influence optical properties in GaAsN alloys.

Findings

L_1c-derived states are crucial for E+ transition formation.

Nitrogen modifies the conduction band significantly.

Nitrogen potential impacts optical properties notably.

Abstract

Optical properties of GaAsN system with nitrogen concentrations in the range of 0.9-3.7% are studied by full-potential LAPW method in a supercell approach. The E+ transition is identified by calculating the imaginary part of the dielectric function. The evolution of the energy of this transition with nitrogen concentration is studied and the origin of this transition is identified by analyzing the contributions to the dielectric function from different band combinations. The L_1c-derived states are shown to play an important role in the formation of the E+ transition, which was also suggested by recent experiments. At the same time the nitrogen-induced modification of the first conduction band of the host compound are also found to contribute significantly to the E+ transition. Further, the study of several model supercells demonstrated the significant influence of the nitrogen potential on the optical properties of the GaAsN system.