PHOTOMODULATION RAMAN-SCATTERING SPECTROSCOPY OF ZNSE GAAS HETEROSTRUCTURE INTERFACE/

Photomodulation Raman spectroscopy is employed to affect and to measur e the band bending at the interface of the heterostructure system ZnSe /GaAs. Our samples are pseudomorphic layers of undoped ZnSe (001) grow n by molecular beam epitaxy (MBE) on undoped GaAs (001) films terminat ed with a 2 x 4 surface reconstruction. The interdiffusion of Zn (Ga) into GaAs (ZnSe) during growth produces an intrinsic band bending at t he interface. The ZnSe overlayer with energy band gap E(Zn-Se) = 2.67 eV offers a transparent window for the photomodulating pumping beam of photon energy E(PM) to reach the heterojunction while the Raman measu rements are in progress. We observed a decrease in the Raman scatterin g intensity of LO(Zn-Se) and an increase in the scattering intensity o f LO(Ga-As) for E(PM) > E(Zn-Se) while almost the reverse behaviour oc curred for E(PM) < E(Zn-Se). These observations are explained in terms of the presence of hole traps at this 2 x 4 reconstructed interface.