Band offsets at interfaces between HgTe, CdTe, and InSb

We have performed self-consistent density-functional calculations in order to determine the electronic structure and band offsets at ideal (110) interfaces between HgTe, CdTe, and InSb. These materials are very nearly lattice matched; strains due to the small lattice mismatch have negligible effects on the lineups. Local-density-functional theory, together with ab initio pseudopotentials, is used to calculate charge densities and potentials for the interface system; this allows us to determine the lineup of the bulk band structures. The following valence-band discontinuities are derived: 0.27 eV for CdTe/HgTe, 0.91 eV for HgTe/InSb, and 1.19 eV for CdTe/InSb. These values obey the transitivity rule. For HgTe/CdTe, we also examined the (100) and (111) interface orientations; the valence-band offset is the same in all cases. We have also used our simpler ‘‘model solid’’ approach to predict the lineups; the results are in very good agreement with those from the self-consistent interface calculations. Noticeable differences are found, however, with values obtained from model theories by Tersoff and by Harrison. Our value for HgTe/CdTe also clearly differs from ΔEv≊0, predicted by the common anion rule. Results for alloys can be obtained by interpolating our results for ΔEv for the pure materials. We discuss how changing the alloy composition x in HgxCd1−xTe/InSb interfaces can result in varying the band offsets over a wide range of values. Finally, we present a discussion of the experimental values that have been reported for HgTe/CdTe, and find good agreement between our theoretical value and the experimental result obtained from photoemission data.