Band-offset trends in nitride heterojunctions

From first principles we have examined the band offsets of selected zinc-blende, wurtzite, and mixed zinc-blende/wurtzite GaN/AlN, GaN/SiC, and AlN/SiC heterostructures, and their dependence on various structural and chemical properties of the interfaces. Contrary to the case of the conventional, small-gap, semiconductor heterojunctions, local atomic interfacial relaxation has a major influence on the offsets of the polar heterovalent nitride systems. However, provided this effect is taken into account, the band-offset dependence on interface orientation, strain, and heterovalency can still be qualitatively explained using linear-response-theory schemes. We also show that a change in the band-gap discontinuity resulting from a cubic (111) to hexagonal (0001) polytype transformation in nitride heterostructures will be selectively found in the conduction-band offset.