COUPLED LO-PLASMON MODES IN SEMIINSULATING GAAS OF ZNSE GAAS HETEROJUNCTIONS/

Raman spectroscopy is used to investigate strong band bending at the i nterface in semi-insulating substrates of ZnSe/GaAs heterostructures g rown at high epitaxy rates. Direct evidence is given of the enhancemen t of polar modes strength, on the substrate side, by the electric fiel d of the space-charge zone associated with Fermi-level pinning. The la tter is qualitatively analyzed by following band flattening under illu mination through the evolution of interfacial coupled LO-phonon-plasmo n modes. Corresponding Raman line shapes are discussed within the phen omenological approach of D. H. Hon and W. L. Faust [Appl. Phys. 1, 241 1 (1973)]. (C) 1996 American Institute of Physics.