Stable partial dislocation complexes in GaN by molecular dynamics and first-principle simulations

Abstract

Wurtzite GaN is a promising material for applications in photoconductive THz radiation sources. For this purpose, the lifetime of photogenerated charge carriers of the order of tenths of picoseconds is required. Controllable lifetime reduction may be considered to achieve by creating recombination active stable dislocation complexes formed by mobile basal-plane Shockley partial dislocations (PDs). In this work, formation pathways and stability of PD complexes in basal planes of wurzite GaN are studied by molecular dynamics (MD) simulations. The simulations reveal the formation of stable complexes by attractive interaction of two 30° or two 90° PDs with opposite Burgers vectors located in neighboring {0001} planes. Ones formed, these complexes change neither their positions, not the atomic configurations during simulations at 1500 K up to 5 ns. The MD results are used as an input for density functional theory calculations to refine the atomic configurations of the complex cores and to investigate their electronic properties. The calculated band structures of GaN with 30°-30° and 90°-90° dislocation complexes exhibit localized energy levels in the band gap near the valence band top and conduction band bottom. Calculations of the local electronic states density confirm the possibility of electron-hole recombination between the states localized at the PD complex cores. These recombination characteristics are distinctly reflected in the calculated absorption spectra. We conclude that creating such PD complexes with required concentrations may be a tool for tailoring the recombination properties of wurtzite GaN for THz radiation generation applications.