Band-edge structure of indium-doped Pb1−xSnxTe across the band-inversion region investigated by the far-infrared magnetoplasma method

Abstract

Far-infrared magnetoplasma spectra in 1 at. % indium-doped ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Sn}}_{\mathrm{x}}$Te single crystals are measured across the band-inversion region (0.15<x<0.40) at temperatures between 4.2 and 20 K, where a large photoconductivity change is observed. From the photocarrier concentration dependences of effective masses, the band-edge mass and the band gap are determined with use of the two-band model. It is found that the band gaps do not change appreciably by doping indium, while the edge masses become much heavier as compared with those of undoped ${\mathrm{Pb}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Sn}}_{\mathrm{x}}$Te. It seems that the band-edge masses and the energy gaps do not reach zero at the band-inversion tin composition (x≃0.35).