Structures and Properties of (ZnS)n(ZnSe)m (n=1–4) Ordered Alloys Grown by Atomic Layer Epitaxy

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Abstract
For the first time, two types of ordered alloys, (ZnS) n (ZnSe)12 n ( n=1–4) and (ZnS)3(ZnSe) m ( m=12–72), were grown on GaAs substrates at low temperature (T=200° 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 n ordered alloys grow coherently with excellent structural and optical properties and exhibit low defect densities.