Strain effects on the energy band-gap in oxygenated CdTe thin films studied by photoreflectance

The incorporation of oxygen during the preparation of sputtered CdTe films produces a strong strain of the zincblende (cubic) lattice. First as a consequence of this, the energy band-gap shifts to lower energies and then, far larger strains, the degeneracy of the hole valence bands splits into two bands at the fundamental band-gap. These two transitions were measured using photoreflectance spectroscopy (PRS) as a function of the oxygen content. The energy band-gap shift resulting from tensile stress in the films was calculated using the elastic constants and deformation potentials for CdTe as well as the measured interplanar spacing values of the (1 1 1) CdTe X-ray diffraction peak. (C) 1999 Elsevier Science Ltd. All rights reserved.