FOURIER RESOLUTION OF SURFACE AND INTERFACE CONTRIBUTIONS TO PHOTOREFLECTANCE SPECTRA OF MULTILAYERED STRUCTURES

A technique for the determination of built-in electric fields by Fouri er transformation of Franz-Keldysh oscillations in photoreflectance (P R) spectra is developed. This technique can be used for the resolution of ''mixed'' PR spectra originating from the surface and buried inter faces of layered semiconductor structures. Fourier transformation is e specially effective in combination with phase-resolved photoreflectanc e, which allows to change the relative amplitude of different PR spect ral components. Model MBE-grown GaAs structures with uniform surface e lectric fields are investigated. Along with the surface PR component, a component originated from the buffer-substrate interface is extracte d by Fourier transformation and phase resolution techniques. The energ y band diagram of the structure is reconstructed. The Fermi level is s hown to be pinned at the buffer-substrate interface by defect-induced electronic states.