LOW TEMPERATURE PHOTOLUMINESCENCE AND RAMAN SCATTERING IN SEMICONDUCTORS

MBE CdTe films grown on (100) InSb at different substrate temperatures are examined by means of low temperature photo- luminescence in the energy range 1.61-1.40 eV. Luminescence spectra are reported for three different energy regions and for substrate temperatures ranging from 170(DEGREES)C to 285(DEGREES)C. The spectral regions are as follows: 1.61 eV to 1.56 eV with exciton emission, 1.56 eV to 1.51 eV with free-to-bound and donor-acceptor pair transitions, and 1.5 eV to 1.4 eV with as yet unidentified lines and a broad band structure. The use of photoluminescence as a means of assessing film perfection is discussed.;To study the effects on the interface caused by the epitaxial growth of insulating films of CaF(,2) on GaAs substrates, Raman scattering and low temperature photoluminescence studies are performed with the wavelength of excitation chosen such that only a shallow layer of the GaAs close to the interface is probed by the optical measurements. The Raman scattering studies on the (100), (111) and (111) verify that the selection rules for allowed scattering are obeyed. A comparison of the LO/TO intensity ratio for the film covered and the bare substrate regions of the GaAs indicate that the epitaxial growth of the insulating films results in changes in the surface states. The photoluminescence spectra indicate that there is no deterioration in the quality of the GaAs substrates as a result of the cleaning procedure. (Abstract shortened with permission of author.);Low temperature photoluminescence and Raman scattering are used to examine the quality of thin films of 3C-SiC grown on (100) Si substrates by a CVD heteroepitaxial technique. The cubic polytype, film orientation and crystal quality are verified by room temperature Raman spectroscopy. Low temperature photoluminescence studies detected nitrogen donor bound excitons, N-Al donor- acceptor pair emission and the D(,I) defect complex in the as grown films of 3C-SiC. A comparison of the luminescence spectra from 3C-SiC films of increasing thickness indicates that quality of the films improves in the region away from the interface. Evidence of strain due to the Si-SiC lattice mismatch is observed in both the Raman and the photoluminescence spectra and the effect of removal of the Si substrate, on these optical spectra is studied.