CHEMICAL AND STRUCTURAL CONTRIBUTIONS TO THE VALENCE-BAND OFFSET AT GAP GAAS HETEROJUNCTIONS/

We report the results of a self-consistent pseudopotential study of th e valence-band offset (VBO) at the lattice mismatched, isovalent GaP/G aAs (001) interface under different strain configurations. The calcula ted value of 0.76 eV for the interface pseudomorphically grown on GaP substrate is in agreement with the experimental data, which are availa ble only for that configuration. The different roles of structure and chemistry on the VBO and its variations with the substrate are discuss ed and a method for separating the corresponding contributions is prop osed. Our results confirm the findings of previous theoretical work on strained heterojunctions, i.e., the variation of the valence-band off set with the lattice constant of the substrate, which for the present system amounts to about 0.4 eV, is essentially due to the strain-induc ed splitting of the topmost valence-band manifold of the two bulk mate rials.