High spin states of cation vacancies in GaP, GaN, AlN, BN, ZnO and BeO: A first principles study

TL;DR

This study uses first principles calculations to analyze high spin states of cation vacancies in various semiconductors, revealing how lattice structure and atomic relaxations influence spin polarization and stability.

Contribution

It provides new insights into the electronic and magnetic properties of cation vacancies in GaP, GaN, AlN, BN, ZnO, and BeO using first principles methods.

Findings

Vacancy-induced levels are in the band gap for GaP, ZnO, BeO.

Stronger exchange coupling in nitrides affects vacancy charge states.

Spin density shape varies with crystal structure.

Abstract

High spin states of cation vacancies in GaP, GaN, AlN, BN, ZnO and BeO were analyzed by first principles calculations. The spin-polarized vacancy-induced level is located in the band gap in GaP, ZnO and BeO. In the nitrides, the stronger exchange coupling forces the vacancy states to be resonant with valence bands, forbids formation of positively charged vacancies in GaN and BN, and allows Al vacancy in p-AlN to assume the highest possible S=2 spin state. The shape of the spin density, isotropic in the zinc blende structure, has a pronounced directional character in the wurtzite structure. Stability of spin polarization of the vacancy states is determined by spin polarization energies of anions, as well as by interatomic distances between the vacancy neighbors, and thus is given by both the lattice constant of the host and the atomic relaxations around the vacancy. Implications for experiment are discussed.