[Study of electroreflectance spectrum and Franz-Keldysh effect at metal-GaAs interfaces]

Electronic properties (electric field, Fermi level pinning and density of interface states) of Au-GaAs, Al-GaAs and Ni-GaAs interfaces were studied by optical methods. These interfaces were fabricated by depositing metals (Ni, Au and Al) on specialized surface-intrinsic-n+ (SIN+) GaAs samples. Electroreflectance (ER) was used to study the electric fields and Fermi level pinnings of metal-GaAs interfaces. Fourier transformation (FT) of ER spectra was used to analyze these interfacial properties. Assuming that only a fraction of the total illuminated area was the effective interface state area, the density of interface states was obtained by measuring the relation between the photovoltage induced by an exciting He-Ne laser beam and the illumination intensity of the laser beam.