Valence Band Structure of (Bi_1–<i>x</i>Sb_<i>x</i>)₂Te₃ Single Crystals

Abstract

Abstract For the first time the anisotropy of reflectivity of polarized infrared light of p‐(Bi 1– x Sb x ) 2 Te 3 single crystals (0.5 ≦ x ≦ 1) is given in the wave number range of 300 to 4000 cm −1 . In addition to the excitation of free carriers in the reflection spectra of the mixed crystals also interband excitations are observed. For the mixed crystals the optical results are consistently described in terms of a six‐valley band model and scattering on acoustical phonons together with the data for the dc conductivity, the Hall coefficients, and the thermopower. The main axis masses m ii , the ellipsoid tilt angle θ, the effective density of states mass m , the cyclotron mass and the susceptibility masses are given in dependence on composition, also the Fermi level E F , the carrier density p , the mobility u ⊥ c , the high frequency dielectric constant ϵ′ ∞ , and the relaxation time τ. The interband influence is interpreted by a simple band model and the energy gap E g calculated.