Structural and electrical characteristics of InSb thin films grown by rf sputtering

Abstract

InSb films have been grown by rf sputtering on cleaved BaF2, CaF2, NaCl, and NaI substrates in addition to polished and annealed (111) -oriented CaF2 wafers. Growth temperatures investigated ranged from 40 to 300 °C, while deposition rates R ranged from 20 to 450 Å/min. The epitaxial temperature for InSb was found to decrease with decreasing deposition rate and decreasing film-substrate lattice mismatch. Stoichiometric single-crystal films were grown on cleaved BaF2 substrates at temperatures as low as 150 °C at R=20 Å/min. Polycrystalline films grown on cleaved CaF2 exhibited a greater degree of preferred orientation than films on polished and annealed CaF2, but the grain size was always less for a given growth temperature. The maximum grain size was related to the film thickness. The electrical properties of 2000-Å-thick polycrystalline InSb films on polished and annealed CaF2 were investigated. The room-temperature electron carrier concentration and Hall mobility of films grown at 300 °C were 4×1017 cm−3 and 200 cm2/V sec, respectively. The dominant charge-scattering mechanism was identified as potential-barrier scattering at either high- or low-angle grain boundaries depending on the grain size of the film.