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)] cal culations have been performed for the [111] ordered common atom strain ed layer superlattices (in particular, the common-anion GaSb/InSb syst em and the common-cation InAs/InSb system). We have focused our attent ion on the potential line up at the two sides of the homopolar isovale nt heterojunctions considered, and, in particular, on its dependence o n the strain conditions and on the strain induced electric fields. We propose a procedure to locate the interface plane, where the band alig nment could be evaluated: furthermore, we suggest that the polarizatio n charges, due to piezoelectric effects, are approximately confined to a narrow region close to the interface and do not affect the potentia l discontinuity. We find that the interface contribution to the valenc e band offset is substantially unaffected by strain conditions, wherea s the total band line up is highly tunable as a function of the strain conditions. Finally, we compare our results with those obtained for t he [001] heterojunctions.