Photoreflectance of indium antimonide

The photoreflectance spectra of $n$-InSb layers were measured using photomodulation Fourier transform infrared spectroscopy. The samples were grown by molecular beam epitaxy on heavily doped $n^+$-InSb(001) substrates annealed under different conditions. The strength of the near-surface electric field was determined from the period of the Franz–Keldysh oscillations observed in the photoreflectance spectra. It was noted that the strength of the electric field increases during a long-term storage of the samples in air. The treatment of $n$-InSb layers in a 1M aqueous solution of Na$_2$S led to an increase in the measured field. Previously, it was shown that, after this treatment, the surface Fermi level is shifted deep into the conduction band and, probably, does not depend on the conditions and time of the preliminary storage of the samples. With the use of passivation in Na$_2$S, the optical method developed in this study allows for the contactless measurement of the concentration of electrons in $n$-InSb homoepitaxial layers.