AN ORDERED GA2TE3 PHASE IN THE ZNTE GASB INTERFACE/

A Ga2Te3 interfacial phase has been observed in a ZnTe/(001)GaSb heter ostructure by high resolution electron microscopy under special imagin g conditions. This phase exists in domains 5-10 nm in size on the ZnTe side of, and usually 2-4 nm away from, the interface. A structural mo del has been proposed for this phase that is derived from the sphaleri te cell with cation sites occupied either fully (occupancy 1) or parti ally (occupancy 5/9) by Ga atoms. The fully occupied Ga sites form a r egular array of uninterrupted chains along the [110] direction of the sphalerite unit cell. The partially occupied Ga sites can also be cons idered as forming chains containing both Ga atoms and vacancies along the [110] direction. Within these chains vacancies are highly mobile, resulting in an average Ga occupancy of 5/9. The unit cell of Ga2Te3 i s orthorhombic with the space group Amm2. The lattice parameters of th e unit cell have been derived from electron diffraction data.