RAMAN CHARACTERIZATION OF ZNSE/GAAS MOVPE HETEROSTRUCTURES

Zinc selenide epilayers on GaAs (100) were grown by the MOVPE technique. Two combinations of source materials were employed. When zinc alkyls and H2Se were used, n-type materials were obtained at low crystal growth temperature (300-degrees-C). When zinc and selenide alkyls were employed, temperatures of 500-degrees-C were needed for growth: in this case, by using a double zone reactor technique, temperatures as low as 300-degrees-C permit the MOVPE growth of ZnSe on GaAs (100). Raman spectroscopy was used for the characterization of ZnSe/GaAs heterostructures in relation to the growth conditions. The activation of the forbidden TO(GAMMA) phonon in ZnSe which is observed in some layers is well correlated with the surface morphology of the epilayers. A weakening of the LO peak of GaAs is correlated with the appearance of a broad and relatively intense band near the TO(GAMMA) phonon frequency in GaAs and is interpreted in terms of a coupled LO phonon-p-type plasmon located at the interface in the GaAs side.