LOW-TEMPERATURE GROWTH OF ZNSXSE1-X ALLOYS FABRICATED BY HYDROGEN RADICAL ENHANCED CHEMICAL-VAPOR-DEPOSITION IN AN ATOMIC LAYER EPITAXY MODE

We have grown ZnSxSe1-x alloys on a GaAs(100) substrate in a wide compositional range (0 less-than-or-equal-to x less-than-or-equal-to 0.3) by the insertion of the ZnSe monolayer into the ZnSe multilayers. We have succeeded in growing these alloys at temperatures as low as 200-degrees-C using the hydrogen radical enhanced chemical vapor deposition (HRCVD) in the atomic layer epitaxy (ALE) mode. In the ALE-HRCVD, it is the self-limiting action, realized on both surfaces covered with Se and Zn, which leads to the high-quality crystals. In the photoluminescence spectra of these ZnSxSe1-x alloys we have observed only the sharp emission lines at the band edges (2.80-2.90 eV) which we attribute predominantly to the excitons. The structural fluctuations have been remarkably reduced by the layer-by-layer method. In addition, we have found very low defect density in these crystals despite the large lattice deformation due to the lattice mismatch. An ordered alloy [(ZnS)2(ZnSe)24]69 has been made by the optimization of the growth conditions.