Defect formation in InSb nanowires and its effect on stoichiometry and carrier transport

This paper presents a study of point defects that exist as a result of non-stoichiometry in InSb nanowires. Using thermodynamics, equilibrium defect concentrations are estimated as a function of antimony vapor pressure. The point defects under study are indium and antimony mono-vacancies and charged versions of these. The magnitude of the defect concentrations is determined by estimating the equilibrium constant for each of the reaction equations, and their values are in agreement with experimental data. At 526 °C, corresponding to the temperature of formation of stoichiometric InSb crystals, the approximate defect concentration is estimated to be of the order of 1018 cm−3. To validate the defect model, InSb nanowires that were ≈10 μm long and had diameters in the range of 40–80 nm, were synthesized by direct antimonidization of In droplets. The nanowire stoichiometry was studied as a function of growth temperature and antimony partial pressure. Our experimental results show that it was essential to maintain an overpressure of antimony-rich vapor for the growth of stoichiometric InSb nanowires. Transport measurements on a single near-stoichiometric InSb nanowire show an electron concentration of ≈2.7 × 1018 cm−3, while the indium-rich InSb nanowires were found to have a higher electron concentration of ≈4 × 1019 cm−3. Metallic In nanowires grown at 600 °C had an electron concentration of ≈1.4 × 1021 cm−3.