Semimetal-semiconductor transition in Bi-In system

Abstract

407-416Semimetal-semiconductor transition in Bi-doped with 4 at. % In single crystal is reported for the first time. Resistivity and Hall coefficient measurements performed on single crystalline sample of Bi-In (4at.%) system for an extensive range of temperature from 4.2-300 K, reveal semiconducting behaviour explicitly in the range 30-130 K. Electronic parameters, i.e. carrier concentration and Hall mobility are calculated for the entire temperature range of 4.2-300 K. The pair of light mass bands at Lc and Lv moves up relative to the Tv band resulting in the disappearance of the overlap between the Lc band and the Tv band and an energy gap of the order of 37.3 MeV is introduced between the light electron (Lc) and heavy hole (Tv) band. Further, the direct band gap between Lc and Lv bands is narrowed to a value of 10.9 MeV in comparison to pure bismuth. An impurity level is also reported on account of doping corresponding to activation energy of 4.1 MeV. Results from microhardness measurements and XRD studies of pure Bi and Bi-In (4 at. %) alloy reveal that In makes complete solid solution with Bi and gains effective entry into the lattice, altering the periodicity of Bloch Potential and modifying the band structure of Bi. This seems to be the reason that the transition from semimetal to semiconductor takes place in the Bi In alloy.</span