In situ monitoring of ZnS/GaP and ZnSe/GaAs metalorganic vapor phase epitaxy using reflectance anisotropy spectroscopy and spectroscopic ellipsometry

Oxide desorption, homoepitaxial m-V buffer growth and the subsequent metalo rganic vapor phase epitaxy of ZnS layers on GaP(001) and ZnSe layers on GaA s(001) were monitored in situ at 350 degrees C using reflectance anisotropy spectroscopy and spectroscopic ellipsometry. Thermal oxide desorption in a II-VI reactor without stabilization by a group V partial pressure leads to rough III-V substrate surfaces with a group VI termination. Application of a proper stabilization induces a well-defined c(4 X 4) and a (2 x 1) surfa ce reconstruction on GaAs and GaP, respectively. Atomic force microscopy pr oves the formation of smooth surfaces with monoatomic steps. Growth of II-V I epilayers was started under various conditions. Anisotropies of the diele ctric function that originate from the II-VI surface or from the buried II- VI/III-V interface were calculated from the reflectance spectra. The separa ted contribution of the interface to the dielectric anisotropy is distinctl y affected by different growth starts particularly for ZnS epilayers on Gap . (C) 2000 Elsevier Science S.A. All rights reserved.