Metalorganic vapour phase epitaxy growth of ZnS layers by (t-Bu)SH and Me2Zn:Et3N precursors

We report for the first time on the metalorganic vapour phase epitaxy of ZnS layers on (100)GaAs substrates by using tertiary-butyl-mercaptan ((t-Bu)SH) and dimethylzinc:triethylamine adduct (Me2Zn:Et3N) as sulphur and zinc precursors respectively. We demonstrate that the combination of Me2Zn:Et3N with (t-Bu)SH avoids the occurrence of pre-reactions even under atmospheric pressure conditions, allowing the growth of good quality single crystalline ZnS epitaxial layers. However, low pressures (~ 300 mbar) were necessary to limit the gas phase depletion of the precursors in the reactor chamber, a consequence of the low thermal stability of (t-Bu)SH and Me2Zn : Et3N. ZnS growth rates as high as 2.4 /~m/h were thus obtained at around 346°C, the growth process being kinetically limited at lower temperatures. The surface of the epilayers was invariably smooth ~ind mirror-like, its average surface roughness being typically around a few nanometres. Finally, no apparent diffusion of Zn and S into the GaAs substrate was observed for samples grown at 350°C, whereas Ga and As were detected into regions of the ZnS epilayers close to the ZnS/GaAs heterointerface.