Microscopic Theory of Electromigration on Semiconductor Surfaces

Electromigration has a dramatic effect on the morphology of semiconductor surfaces, inducing, for example, step bunching instabilities. To explain these phenomena from a microscopic point of view, we study self-diffusion on Si(111) through first principles calculations, and propose a mechanism for diffusion bias induced by external electric fields. A competing, wind-force effect arises from enhanced surface electron density, due to incomplete melting. The competition leads to two transitions in surface kinetics with increasing temperature, in agreement with experimental observations.