Lack of Band-Offset Transitivity for Semiconductor Heterojunctions with Polar Orientation: ZnSe-Ge(001), Ge-GaAs(001), and ZnSe-GaAs(001)

The fabrication of pseudomorphic Ge layers in the interface region of ZnSe-GaAs heterostructures was recently shown to be an effective method of reducing the overall valence-band discontinuity. We investigate here the microscopic mechanism behind this effect, drawing on measurements and theoretical calculations of the band offsets for individual isolated heterojunctions between the different semiconductor constituents. We find that the formation of different interface configurations in individual neutral heterojunctions can account for the observed deviations from the predictions of the transitivity rule and hence for the effect of Ge interlayers.