ULTRAVIOLET QUANTUM-WELL STRUCTURES BASED ON ZNS/ZNS1-XSEX AND ZNS/ZN1-XCDXS MULTILAYERS GROWN BY MOLECULAR-BEAM EPITAXY

Multilayers of ZnS/ZnS1-xSex and ZnS/Zn1-xCdxS were successfully grown by molecular-beam epitaxy using elemental sources. Photoluminescence (PL) experiments were performed at 4.2 K to evaluate the optical quality and carrier-confinement properties of these multiple-quantum-well structures. In general, the emission peaks from the ZnS/Zn1-xCdxS samples were much sharper and more intense than those from ZnS films or ZnS/ZnS1-xSex multilayers. These PL characteristics indicate improved electron confinement in the Cd-based wells, implying that an appreciable conduction band offset exists between ZnS and Zn1-xCdxS. This work suggests that ZnS/Zn1-xCdxS quantum-well structures may play an important role in the development of ultraviolet (UV) and near-UV light emitting structures.