Valence-band offsets at the ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{0.5\mathrm{-}\mathrm{x}}$${\mathrm{In}}_{0.5}$P-ZnSe(001) lattice-matched interface

The difficulty in making good Ohmic contact at the interfaces with p-doped ZnSe is an important problem hindering the realization of blue-light-emitting diode lasers based on the II-VI semiconductor technology. So far no metal or semiconductor material has been found to have a low enough barrier at the (001) interface with ZnSe. A possible solution to this problem is the insertion of a so-called barrier-reduction layer at the interface with ZnSe. We have investigated the interface formation energies and valence-band offsets at the (001) interface between ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{0.5\mathrm{-}\mathrm{x}}$ ${\mathrm{In}}_{0.5}$P and ZnSe. The results of our calculations show the existence of a strong interdependence between the valence-band offset and the interface geometric structure. The interface is found to have structural and electronic similarities to the GaAs-ZnSe(001) system. The very low values obtained for the valence-band offset confirm the possibility of using this material as a major constituent of the barrier-reduction layer.