Surface structure of Zn- or Se-treated GaAs(001) and its influence for ZnSe heteroepitaxy

The surface structures of Se- or Zn-treated GaAs(001) have been investigated using scanning tunneling microscopy, X-ray photoelectron spectroscopy, and reflection high-energy electron diffraction connected to a dual chamber MBE system. The influence of controlled CaAs surface for the initial stage of ZnSe heteroepitaxy has also been studied. A (2 x 1) structure was generated by Se-exposure on both As- and Ga-stabilized GaAs(001) surface. This is recognized as a result of the reaction between Se and Ga. In the case of Zn-exposure on (2 x 4) surfaces, the change of RHEED intensity and XPS measurement suggested Zn deposition but there were no obvious changes in the STM images, During the ZnSe growth on a Se-terminated GaAs-(2 X 1) surface, RHEED patterns immediately became spotty and a disordered rough surface was observed by STM, On the other hand, during ZnSe growth on the Zn-treated GaAs-(2 X 4) surface, RHEED patterns were streaky from the very beginning. We could also successfully obtain STM images of a Se-stabilized ZnSe(001)-(2 X 1) reconstruction and this means that well-ordered surfaces were obtained as a result of layer mode growth using the Zn-treatment.