| Compound semiconductor thin films grown epitaxially on thick substrates are of great interest in modern electronics and material science and technology. A number of special systems such as 3C-SiC/Si and CdTe/InSb or CdTe grown by CVD. MBE, MOCVD and UHV-SD techniques are studied experimentally by room temperature (RT) Raman scattering and low temperature (LT) photoluminescence (PL) spectroscopies.;A series of RT Raman and LT-PL spectra of CVD 3C-SiC/(100)Si are obtained. Some unusual features of these Raman and PL spectral studies are reported and discussed. A new method for the determination of Raman cross sections is suggested. A method for calculating the stress and strain in thin films on thick substrates is proposed and applied to the CVD SiC/Si samples. The large release of the SiC/Si interface strain due to misfit dislocations is discussed. Dislocations and other line defects related PL spectral features are reported.;On the basis of our earlier publications on CdTe thin films, some further PL studies on CdTe thin films grown by MBE, MOCVD and UHV-SD on InSb and CdTe substrates were undertaken. The surface preparation of the (001) InSb substrate and the subsequent MBE growth of CdTe are studied by LT-PL and X-ray double crystal rocking curves (DCRC). The optimum substrate surface preparation conditions, including the ion beam incident angle, bombardment cleaning time and temperature, are obtained. Finally, we compare the spectra obtained from the growth of excellent quality CdTe thin films using MBE, MOCVD and UHV-SD. The bound exciton line widths and the radiative defect densities obtained from these PL spectra are sharper and smaller by an order of magnitude from those far reported in the literature. (Abstract shortened with permission of author.);The differences of the lattice constants and thermal coefficients between the film and the substrate lead to stresses and strains in the thin film and the interface region. These stresses and strains will shift or split the energy bands and phonon modes, and exert influences on the luminescence and Raman spectra. A theoretical discussion is given for a generalized axial stress and its effects on energy band gap shifts and Raman phonon shifts. |
