Point defects in M_{2 – x}In_xTe₃ (M = Sb or Bi) crystals

Abstract

Spectral dependences of the reflectance R in the plasma-resonance frequency range have been measured on (0001) cleavage faces of Sb_2–x In _x Te₄ (x = 0·0–0·41) single-crystal samples grown from elements of 99·999% purity by means of a modified Bridgman technique. The plasma-resonance frequency (and hence the concentration P of holes) has been determined from the interpretation of the experiment R = f(v) curves. The dependence on P on the content of In atoms shows a monotonic decrease from a value of 6–4 x 10²⁵ m₋₃ for x = 0 to 1 × 10²⁵ m ₋₃ for x = 0·41. The account for the decrease in the concentration of holes, we propose a model based on the assumption that the introduction of In atoms into the crystals results in a decrease in the concentration of antisite defects and, at the same time, in a change in the concentration of vacancies in the Te sublattice of Sb₂Te₃ crystals. The P = f(x) dependence for Sb_2–x In_xTe₃ crystals is compared with the variation in the concentration of free charge carriers with In content in Bi_{2 – x} In _x Te₃ crystals.