Electronic structure of GaAs1-xNx alloy by soft-X-ray absorption and emission: Origin of the reduced optical efficiency

TL;DR

This study uses soft-X-ray absorption and emission spectroscopy to analyze the local electronic structure of nitrogen in GaAsN alloys, revealing charge transfer effects that limit optical efficiency, and discovering a k-conserving scattering process.

Contribution

First detailed spectroscopic analysis of N electronic structure in GaAsN alloys, identifying charge transfer as a key factor in optical efficiency reduction.

Findings

Charge transfer from N atoms reduces wavefunction overlap in conduction band.

Dramatic deviations from crystalline GaN in electronic structure.

Discovery of a k-conserving resonant inelastic x-ray scattering process.

Abstract

The local electronic structure of N atoms in a diluted GaAs1-xNx (x=3%) alloy, in view of applications in optoelectronics, is determined for the first time using soft-X-ray absorption (SXA) and emission (SXE). Deviations from crystalline GaN, in particular in the conduction band, are dramatic. Employing the orbital character and elemental specificity of the SXE/SXA spectroscopies, we identify a charge transfer from the N atoms at the valence band maximum, reducing the overlap with the wavefunction in conduction band minimum, as the main factor limiting the optical efficiency of GaAs1-xNx alloys. Moreover, a k-conserving process of resonant inelastic x-ray scattering involving the L1 derived valence and conduction states is discovered.