Effects of boron and arsenic doping in β-FeSi2

Abstract

The effects of boron and arsenic doping in β-FeSi2 have been studied by theoretical simulations and electrical characterization. First-principles calculations revealed that B and As were energetically favorable to occupy the SiII and SiI sites, respectively. The impurity doping was found to induce structural relaxation via lattice distortion, with As doping causing elongation of the As­Si bonds and contraction of the As–Fe bonds while B doping resulting in both inward and outward relaxations of the neighboring Si and Fe host atoms. p-type and n-type conductivities were suggested for the B- and As-doped β-FeSi2, respectively, and confirmed experimentally by Hall effect measurements. B and As were shown to introduce shallow impurity levels in the forbidden gap of β-FeSi2 and therefore could be effective dopants for β-FeSi2. A carrier concentration in a tunable range of 1017 cm−3 and a mobility in the order of 100 cm2/V s were consistently obtained.