STRUCTURES AND PROPERTIES OF (ZNS)N(ZNSE)M (N=1-4) ORDERED ALLOYS GROWN BY ATOMIC LAYER EPITAXY

For the first time, two types of ordered alloys, (ZnS)n(ZnSe)12n (n=1-4) and (ZnS)3(ZnSe)m (m=12-72), were grown on GaAs substrates at low temperature (T=200-degrees-C) by atomic layer epitaxy (ALE). Hydrogen-radical-enhanced chemical vapor deposition (HRCVD) was used to deposit the atomic layers. Layered structures were confirmed by X-ray diffraction of the deposited films, which showed satellite peaks at the expected values. Photoluminescence (PL) measurements indicate a high quantum efficiency with a single, narrow emission band near the bandgap energy. Despite the large lattice deformation, deep-level emission intensity was negligible in a wide compositional range of the ordered alloys, (ZnS)3(ZnSe)m. The photoluminescence peak energies shift systematically with changes in the selenium-to-sulfur ratio of these ordered alloys. The (ZnS)n(ZnSe)12, ordered alloys grow coherently with excellent structural and optical properties and exhibit low defect densities.