Piezospectroscopy and first-principles calculations of the nitrogen-vacancy center in gallium arsenide

TL;DR

This study combines piezospectroscopy and first-principles calculations to analyze the nitrogen-vacancy center in gallium arsenide, revealing its symmetry, isotope effects, and stability, with implications for understanding defect structures in semiconductors.

Contribution

The paper provides the first combined experimental and theoretical analysis of the NV center in GaAs, confirming its symmetry and structural relaxation through advanced techniques.

Findings

NV center exhibits C₃v symmetry in GaAs.

Isotope effects cause fine structure and non-linear stress shifts.

First-principles calculations agree with experimental observations.

Abstract

The nitrogen-vacancy (NV) center occurs in GaAs bulk crystals doped or implanted with nitrogen. The local vibration of nitrogen gives rise to a sharp infrared absorption band at 638 cm$^{-1}$, exhibiting a fine structure due to the different masses of neighboring $^{69}$Ga and $^{71}$Ga host isotopes. Piezospectroscopic investigations in the crystallographic <100> direction prove that the center has C$_\text{3v}$ point symmetry, which is weakly perturbed by the isotope effect. The stress-induced shifts of some band components show an unusual non-linear behavior that can be explained by coupling between the isotope and the stress splitting. First-principles density-functional theory calculations are in full accordance with the experiments and confirm the C$_\text{3v}$ symmetry, caused by relaxation of the nitrogen atom from the anion lattice site towards the nearest-neighbor Ga plane. The NV center in GaAs is structurally analogous to the same center in diamond. The $-3$ charge state is most stable for nearly all Fermi-level positions.