Coupled LO–plasmon modes in semi-insulating GaAs of ZnSe/GaAs heterojunctions

Abstract
Raman spectroscopy is used to investigate strong band bending at the interface in semi‐insulating substrates of ZnSe/GaAs heterostructures grown at high epitaxy rates. Direct evidence is given of the enhancement of polar modes strength, on the substrate side, by the electric field of the space‐charge zone associated with Fermi‐level pinning. The latter is qualitatively analyzed by following band flattening under illumination through the evolution of interfacial coupled LO‐phonon–plasmon modes. Corresponding Raman line shapes are discussed within the phenomenological approach of D. H. Hon and W. L. Faust [Appl. Phys. 1, 241 (1973)].