EFFECT OF INTERFACIAL BOND TYPE ON THE ELECTRONIC AND STRUCTURAL-PROPERTIES OF GASB INAS SUPERLATTICES/

We have investigated the effects of interfacial bond configuration on the electronic and structural properties of thin (001)GaSb/InAs superl attices by using state-of-the-art ab initio molecular dynamics techniq ues to calculate the electronic and structural properties of two twelv e-atom model GaSb/InAs superlattices which have been constructed to co ntain only In-Sb (model 1) or Ga-As (model 2) interface bonds, respect ively. We find the strain at the the interface to be different in the two cases. In model 1, the In and Sb atoms at the interface move away from each other toward the InAs and GaSb layers, respectively, increas ing the interfacial separation (4.3 % greater than in bulk InSb) and c ompressing the back bonds to the atoms in the layer below the interfac e. In model 2 the Ga and As atoms move toward each other, decreasing t he interplanar separation at the interface (3.2% smaller than in bulk GaAs) and stretching the back bonds to the neighboring Sb and In atoms , respectively. We calculate the valence band offset for the Ga-As bon ded structure to be 0. 15 eV smaller than that for the model containin g only In-Sb bonds. This smaller band offset leads to more mixing of A s p character into the highest lying valence band of the superlattice and results in a 0.015 eV smaller spin-orbit splitting at the valence band edge of the Ga-As bonded structure. This result is consistent wit h the 0.05 eV larger band pp observed for Ga-As bonded structures in r ecent photoconductivity measurements made on both Ga-As and In-Sb bond ed samples grown by molecular-beam epitaxy.