Strain-dependence of Te interstitial diffusion in CdTe

CdTe is an attractive absorber material for solar cell applications due to its optimal bandgap and high absorption coefficient. One area of particular interest is the diffusion of defects such as Te interstitials, since this affects the thin-film quality and composition during processing.

Here we present the results of molecular dynamics (MD) simulations of Te interstitial diffusion in zincblende CdTe for values of the triaxial strain ranging from -2% (compressive) strain to +2.8% (tensile) strain. By carrying out MD simulations of Te interstitial diffusion over a range of temperatures, and then carrying out Arrhenius fits, we have determined the effective activation barrier and prefactor for each value of the global strain.

We find that both activation energy and pre-factor exhibit non-monotonic behavior, increasing with both compressive and tensile strain. We also present an analysis of the key diffusion pathways for 3 different values of the strain which explains the non-monotonic strain dependence obtained in our simulations. Our results also indicate that in each case, the diffusion of interstitial Te involves a variety of concerted events with a wide range of activation barriers.