Reflectivity of iodine-doped Sb2Te3 crystals

The wavelength dependence of the reflectivity R(λ) has been investigated in the plasma resonance frequency region on Sb2Te3 single crystals using polarized light for E ∥ c and E ⟂ c directions. From these results the ratio of the effective masses for parallel and perpendicular directions with respect to the c-axis m∥c/m⟂c is determined which is equal to (2.8 ± 0.3) at 294 K. From the measured values of the Hall voltage, thermoelectric power, and electrical conductivity, using a six-valley model suggested for the interpretation of the properties of p-Sb2Te3 under specific conditions mentioned in this paper, the transport quantities were determined both for “pure” Sb2Te3 crystals and for Sb2Te3 (I) crystals. Following values were obtained for “pure” single crystals of Sb2Te3: concentration of holes N = 1.5 × 1020 cm−3, mobility μ⟂c = 168 cm2 V−1 s−1, effective mass m*⟂c = 0.21, m*∥c = 0.59, relaxation time 〈τ〉⟂c(opt.) = 2 × 10−14 s, 〈τ〉⟂c(cond.) = 2 × 10−14 s.