Optical and opto-electronic properties of polycrystalline Cd0.96Zn0.04Te thin films

Abstract

Cd0.96Zn0.04Te thin films are deposited onto thoroughly cleaned glass substrates (Coming 7059) kept at room temperature by vacuum evaporation. The films are found to have good stoichiometry as analyzed by Rutherford Backscattering Spectrometry. The films exhibited zinc blende structure with predominant (111) orientation. The surface morphology of the films is studied by Atomic Force Microscopy. The rms roughness of the films evaluated by AFM is 3.7 nm. The pseudodielectric-function spectra, epsilon(E) = epsilon(1)(E) + i epsilon(2)(E) at room temperature are measured by spectroscopic ellipsometry. The measured dielectric function spectra reveal distinct structures at energies of the E-1, E-1+Delta(1) and E-2 critical points. The band gap energy of the films measured by optical transmittance measurement is 1.523 eV. The PL spectrum of the films shows intense emission due to free and bound exciton recombination and no emission associated with crystal imperfection and deeper impurity levels. The PL line shapes give indications of the high quality of the layers.