Electric Field Effect on the Absorption Edge in SbSI

The shift of the absorption edge of SbSI due to the application of an electric field was measured as a function of field strength, temperature, and the wavelength of an incident light beam. The results qualitatively agree with Harbeke's results. Based on a phenomenological discussion, we obtain a relation E g=E g0+p P x+β x P 2, where E g is the band edge energy at which the absorption coefficient is 150 cm-1, x the strain, P is an electric polarization, p P a constant, and β x the polarization potential for the bound crystal. This relation can explain the field and temperature dependence of the edge shift.