Formation of a thin III-VI compound interfacial layer at ZnTe/ZnSe heterojunction and its effect on energy band discontinuity

Interfacial layers were inserted at the interface of ZnSe and ZnTe in order to reduce both (1) the effect of strain and (2) the valence band discontinuity. The interfacial layer adapted in this study is the III-VI compound (Ga,Se). The layered structure GaSe is favorable for the present work, because it can be a buffer layer to relax the lattice mismatch at the interface. All layers including ZnTe, (Ga,Se) and ZnSe were grown on (100) GaAs substrate by conventional molecular beam epitaxy. The crystal structure of the (Ga,Se) on ZnSe was investigated. The growth of the layered structure GaSe layer on (100) ZnSe was very difficult, though the defect zinc-blende structure Ga₂Se₃ layer could be easily grown. The defect zinc-blende structure Ga₂Se₃ was inserted at the interface of ZnSe and ZnTe so that the valence band discontinuity could be modified. The discontinuity was decreased to about 0.1 eV when the thickness of the interfacial layer was about 8Å. The current-voltage characteristics were measured for the sample with Ga₂Se₃ interfacial layer. The structure with Ga₂Se₃ exhibited the ohmic property. These results suggest that the valence band discontinuity between ZnTe and ZnSe can be reduced by introducing the Ga₂Se₃ interfacial layer.