MICRO-RAMAN-SCATTERING STUDY OF SURFACE-RELATED PHONON MODES IN POROUS GAP

Porous GaP layers prepared by electrochemical dissolution of (100)-ori ented bulk material have been studied by micro-Raman spectroscopy. The anodization causes a breakdown of the polarization selection rules, i nherent to a (100) surface, accompanied by a downward shift of the LO- phonon frequency and by the appearance of a surface-related vibrationa l mode in the gap between the bulk optical phonons. The frequency of t he surface-related mode was found to decrease from 398 to 394.3 cm(-1) with increasing anodization current. A Raman line-shape analysis base d on the light scattering due to the electro-optic and deformation pot ential mechanisms is presented.