Incorporation of divalent transition-metal ions in bulk In2O3 single crystals grown from the melt and their impact on optical and electrical properties

Abstract

Bulk In2O3 single crystals were grown directly from the melt by the novel method named “Levitation-assisted self-seeding crystals growth method,” as we described in detail elsewhere in Galazka et al., J. Cryst. Growth 388, 61–69 (2014). The crystals were doped with Mg, Zn, Ni, and Co with the same concentrations in the starting composition to compensate for residual free carriers in bulk crystals. The crystals were grown in the same furnace configuration and under the same growth conditions. As-grown crystals revealed the electrical resistivity of 2–4 × 10−2 Ω cm for undoped and Zn-doped and 104 Ω cm for Mg-, Ni-, and Co-doped In2O3 crystals. After annealing in an atmosphere containing oxygen at 700–900 °C, there was a minor change in the resistivity of the undoped and a significant increase up to 102 and >108 Ω cm for In2O3:Zn and In2O3:Mg, Ni, and Co, respectively. The electron mobility increased from 150–160 to 250 cm2 V−1 s−1 for undoped and decreased to 30–60 cm2 V−1 s−1 for In2O3:Zn after annealing at 900 °C in the atmosphere containing oxygen. After annealing, transmittance spectra have significantly improved for undoped and In2O3:Zn crystals, remained substantially unchanged for In2O3:Mg, and deteriorated for Co- and Ni-doped In2O3 crystals.