Zn preadsorption on GaAs(100)2×4 prior to ZnSe growth

We report here a systematic study of the adsorption of Zn on GaAs(100)2×4 prior to ZnSe growth. At the typical ZnSe growth temperature of 290 °C, the Zn coverage was found to increase only logarithmically with increasing exposure time, so that only submonolayer coverages of Zn can be absorbed and remain stable on the GaAs substrates. At room temperature, and in general at temperatures below 150-200 °C, a drastic increase in the Zn sticking coefficient makes monolayer and multilayer adsorption possible. However, subsequent annealing at the ZnSe growth temperature removes most of the Zn atoms from the surface, so that only submonolayer coverages are found on the initial growth surface. We discuss the possible role of Zn as an interface control layer between ZnSe and GaAs in the light of our results.