EPITAXIAL-GROWTH OF ZNS GROWN AT LOW-TEMPERATURES BY ATMOSPHERIC-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY

Single crystalline epitaxial layers of undoped ZnS have been grown at 250-300°C on (100)-oriented GaAs substrates by atmospheric pressure metalorganic vapor phase epitaxy using dimethylzinc (DMZ) and hydrogen sulfide as source materials. The premature reaction typically encountered with this source combination can be eliminated completely as well as in the case of ZnSe epitaxial growth using DMZ and hydrogen selenide, even at atmospheric pressure, by controlling the source gas velocity and the mole ratio. ZnS heteroepitaxial layers (heteroepilayers) with excellent mirrorlike surface morphologies, which were grown at 250°C for the source gas mole (VI/II) ratio below 10, were obtained. The VI/II ratio dependence of the ZnS heteroepilayers is very different from that of ZnSe heteroepilayers, whose surface morphologies are mirrorlike at a VI/II ratio above 10. Also the surface morphologies of the ZnS heteroepilayers gradually begin to degrade as the growth temperature increases above 250°C. Moreover, below 220°C, the crystalline quality abruptly changes to polycrystal, as with bad hazy morphology, which is similar to that seen in ZnSe heteroepilayers grown below 210°C. It is shown that it is necessary to grow ZnS layers epitaxially at least higher than 220°C.