Electric fields and valence-band offsets at strained [111] heterojunctions

Ab initio full-potential linearized augmented plane wave (FLAPW) [H. J. F. Jansen and A. J. Freeman, Phys. Rev. B 30, 561 (1984); M. Weinert, H. Krakauer, E. Wimmer, and A. J. Freeman, ibid. 24, 864 (1981)] calculations have been performed for the [111] ordered common atom strained layer superlattices (in particular, the common-anion GaSb/InSb system and the common-cation InAs/InSb system). We have focused our attention on the potential line up at the two sides of the homopolar isovalent heterojunctions considered, and, in particular, on its dependence on the strain conditions and on the strain induced electric fields. We propose a procedure to locate the interface plane, where the band alignment could be evaluated; furthermore, we suggest that the polarization charges, due to piezoelectric effects, are approximately confined to a narrow region close to the interface and do not affect the potential discontinuity. We find that the interface contribution to the valence band offset is substantially unaffected by strain conditions, whereas the total band line up is highly tunable as a function of the strain conditions. Finally, we compare our results with those obtained for the [001] heterojunctions.