Can We Tune the Band Offset at Semiconductor Heterojunctions?

Abstract

The long-standing problem of determining which interface-specific properties affect the band offset at semiconductor heterojunctions is readdressed using a newly developed theoretical approach. The actual interface is considered as a perturbation with respect to a reference periodic system (virtual crystal). By comparison with state-of-the-art self-consistent calculations, we show that linear-response theory provides a very accurate description of the electronic structure of the actual interface in a variety of cases, and sheds light on the mechanisms responsible for the band offset. Results are presented for a number of lattice-matched junctions, both isovalent and heterovalent. It is shown that—within linear response theory—band offsets are genuine bulk properties for isovalent interfaces, whereas they do depend on the atomic structure of the junction for polar interfaces between heterovalent semiconductors. In the latter case, however, the interface-dependent contribution to the offset can be calculated—once the microscopic geometry of the junction is known—from such simple quantities as the lattice parameters and dielectric constants of the constituents. Perspectives for extending the theory to non-lattice-matched systems are also briefly discussed.