In situ reflectance-difference spectroscopy of doped CdTe and ZnTe grown by molecular beam epitaxy

We have used reflectance-difference (RD spectroscopy (UW-visible energy ran ge) during the growth and doping process of CdTe(001) and ZnTe(001) layers by molecular beam epitaxy (MBE), The MBE chamber is equipped with an electr on cyclotron resonance cell to generate N plasma and a ZnCl2 effusion cell for the p- and n-type doping, respectively. After the first stages of the g rowth and prior doping, different spectral features were found as we change d from Cd or Zn to Te stabilized conditions due to surface anisotropy. Howe ver, as the doping of the growing layer further increased, the RD spectra o f both surfaces showed resonances around E-1 and E-1+Delta(1) interband tra nsitions due to the linear electro optic (LEO) effect, Although RD spectra exhibit similar line shapes dominated by surface transitions, differences d ue to the LEO can be isolated. Different Fermi level pinning mechanisms are proposed for both materials because the RD measurements of the LEO strongl y depend on surface termination. (C) 2000 American Vacuum Society. [S0734-2 11X(00)06704-4].