THE ABSOLUTE EFFICIENCY OF RESONANT RAMAN-SCATTERING BY LONGITUDINAL OPTICAL PHONONS IN ZNTE NEAR THE E(0) GAP

The absolute efficiency of resonant Raman scattering by longitudinal o ptical phonons is determined for an orientated ZnTe bulk crystal and s ingle-crystalline ZnTe epilayers with incident photon energies near th e E0 band gap at a temperature of 2 K. The ZnTe layers were grown by m etal-organic vapour-phase epitaxy (MOVPE) on (001) GaAs and (001) GaSb , respectively, with a thickness of about 2 mum. Absolute values of th e Raman scattering efficiency (RSE) have been determined in z(x, x)zBA R and z(y, x)zBAR backscattering configuration using a sample-substitu tion method and correcting the measured intensities with respect to ab sorption, reflection, and refraction. Measurements of the absorption c oefficient and the reflectivity were performed on the same samples and at the same temperature. Well resolved maxima of the RSE appear at th e m = 1 and m = 2 discrete energy levels of the band-gap exciton for i ncoming resonance and at the m = 1 level for outgoing resonance. Valen ce-band splitting due to residual biaxial strain in the ZnTe epilayers results in a splitting of the m = 1 resonance maximum for both incomi ng and outgoing resonance.