Density-functional calculations of carbon diffusion in GaAs

Self-consistent-charge density-functional tight-binding (SCC-DFTB) calculations have been performed to survey the potential-energy surface for a single interstitial carbon atom introduced into GaAs. The results provided a possible model for the diffusion of carbon through GaAs with an activation energy of less than 1 eV. The carbon atom moves via split-interstitial and bond-centered configurations. Subsequently, the energetics of the model reaction were refined using a fully self-consistent density-functional method, AIMPRO. These calculations were found to be in good agreement with the more approximate SCC-DFTB results. Experimental studies have also found an activation energy of ~1 eV for carbon migration in heavily doped material.