Optical transmission of Bi/1-x/Sb/x/ semiconductor solid solutions

The experimental technique is described and results are presented for an investigation of the optical transmission of thin single-crystal Bi(1-x)Sb(x) films with x of 10.3 to 18 at % in the wavelength range between 50 and 130 microns at a temperature of 4.2 K. Lattice absorption bands are observed. The dependences of the refractive index and optical width of the forbidden band on antimony content are determined on basis of the interference fringes of the transmission spectrum and the fundamental absorption edge. For the x values indicated, the refractive index varies between 11.8 and 13.7, while the optical width of the forbidden band varies between 10.5 and 20 MeV.