Transport properties of n- and p-type polycrystalline BaSi2

Abstract

Electron and hole mobilities versus temperature in semiconducting barium disilicide (BaSi2) have been systematically studied both experimentally and theoretically. The experiments were performed with undoped 250 nm-thick BaSi2 polycrystalline films grown by molecular beam epitaxy. The grain size of films ranged from 0.2 to 5 μm with the electron concentration of 5.0 × 1015 cm−3. To investigate the hole mobility, B-doped p-BaSi2 films with various dopant concentrations were fabricated and studied. The experimental temperature dependence of the electron mobility in the range of 160–300 K was found to have a maximum of 1230 cm2/V∙s at 218 K, while at room temperature (RT) it dropped down to 816 cm2/V∙s. We demonstrate that the temperature dependence of the electron mobility cannot be adequately reproduced by involving standard scattering mechanisms. A modified approach accounting for the grained nature of the films has been proposed for the correct description of the mobility behavior. The highest hole mobility in p-BaSi2 films reaching ~ 80 or 200 cm2/V∙s (for the films grown on (111) or (001) Si substrates, respectively) at RT is about an order or four times of magnitude smaller than that in n-BaSi2 films. Such a great difference we ascribe to the specific features of electron-phonon and hole-phonon coupling in semiconducting BaSi2.