DIFFERENTIAL REFLECTANCE SPECTROSCOPY OF GAALAS THIN-FILMS AND GAAS BULK UNDER EXTERNALLY APPLIED TEMPERATURE-GRADIENT

Using vibrating optical beam, differential reflectance (DR) spectra ha ve been obtained on GaAlAs thin films and GaAs bulk subjected to an ex ternally applied temperature gradient. The DR spectra reveal all the c ritical points, namely, E-0 and E-0 + Delta(0) in GaAlAs and E-0, E-0 + Delta(0) and E-1 in GaAs in the given energy range under study where as, without the temperature gradient, DR spectra measured on homogeneo us materials are structureless. The DR technique shows better sensitiv ity than photoreflectance on thin epilayers. Our investigation suggest s that, combined with the application of a field gradient, DR can be m ade extremely useful for the characterization of semiconductors. (C) 1 997 American Institute of Physics.