Contactless Measurement of Electron Concentration in Undoped Homoepitaxial InSb Layers

Abstract

The photoreflectance spectra of undoped InSb grown by the molecular beam epitaxy method on the n⁺-InSb substrate have been measured with a Fourier-transform infrared (FTIR) spectrometer. The intensity of the surface electric field has been determined from the period of the Franz–Keldysh oscillations observed at low temperatures. Since the value of the Fermi level pinning has been stabilized by treating the samples in an aqueous solution of Na₂S, the field intensity depends mainly on the concentration of free carriers. The influence of the temperature of preliminary annealing of the substrate on the electron concentration in the epitaxial layer has been observed.