Interfacial segregation and electro-diffusion of dopants in superlattices

A first-principles theory of interfacial segregation of dopants and defects in heterostructures is developed and applied to GAN/A1N superlattices. The results indicate that the equilibrium concentrations of a dopant at two sides of an interface may differ by up to a few orders of magnitude, depending on its chemical identity and charge state, and that these cannot be obtained from calculations for bulk constituents alone. In addition, the presence of an internal electric field in polar heterostructures induces electro-migration and accumulation of hydrogen at the appropriate interfaces.