Photomodulation Raman scattering spectroscopy of ZnSeGaAs heterostructure interface

Photomodulation Raman spectroscopy is employed to affect and to measure the band bending at the interface of the heterostructure system ZnSeGaAs. Our samples are pseudomorphic layers of undoped ZnSe (001) grown by molecular beam epitaxy (MBE) on undoped GaAs (001) films terminated with a 2 × 4 surface reconstruction. The interdiffusion of Zn (Ga) into GaAs (ZnSe) during growth produces an intrinsic band bending at the interface. The ZnSe overlayer with energy band gap EZn-Se = 2.67 eV offers a transparent window for the photomodulating pumping beam of photon energy EPM to reach the heterojunction while the Raman measurements are in progress. We observed a decrease in the Raman scattering intensity of LOZnSe and an increase in the scattering intensity of LOGaAs for EPM > EZn-Se while almost the reverse behaviour occurred for EPM < EZn-Se. These observations are explained in terms of the presence of hole traps at this 2 × 4 reconstructed interface.