Extrinsic levels, diffusion, and unusual incorporation mechanism of lithium in GaN

TL;DR

This study uses first-principles calculations to explore lithium's behavior in GaN, revealing its diffusion, transformation into a Ga-substitutional acceptor, and its role as an electron sink with specific ionization levels.

Contribution

It provides new insights into lithium's diffusion mechanisms, transformation processes, and electronic levels in GaN through first-principles analysis.

Findings

Li diffuses at temperatures above 600 K.

Li can transform into a Ga-substitutional acceptor via recombination with Ga vacancies.

Li acts as an electron sink with shallow ionization levels.

Abstract

Results of a first-principles study of the Li impurity in GaN are presented. We find Li is a channel interstitial, with an onset for diffusion at T$\sim$ 600 K. Above this temperature, Li can transform to a Ga-substitutional acceptor by exothermic recombination with Ga vacancies. This process implies capture of at least one electron; therefore Li acts as an electron sink. Li$_{\rm Ga}$ is stable again interstitialcy, and has a shallow first ionization levels of 0.16 eV, and second ionization at 0.63 eV. Lattice locations and their temperature dependence are in close agreement with recent experiments.