The epitaxial growth of thick smooth films of ZnS on GaAs

The growth of smooth thick (80 μm) films of highly-ordered ZnS on GaAs substrates [oriented near the (100)] by open tube vapour transport in H₂:HCl gas flow has been investigated. We have found the surface features of the layers to be similar to those associated with GaAs epitaxy, particularly the “sand-dune” type of hillock. To obtain smooth layers, the substrates must be off the (100) plane, and precleaned in HCl acid. The most critical factor during growth was the HCl transport gas concentration (1.2-1.4%). We have investigated the influence of growth parameters on surface quality and Si contamination. The Si concentration in the films was found to be approximately directly proportional to the growth rate of the layers.