Band Structure of Gallium-Doped Germanium Crystal

Abstract

The germanium which is a semiconductor at room temperature becomes superconducting below a transition temperature of 0.5 K by doping with gallium in tetrahedral interstitial sites. We introduced several models of the Ga‐doped Ge (Ge:Ga) through the substitution of the Ga atom into the supercell of Ge crystal. We employed all electron calculation instead of the plane wave method to treat the electrons in the atoms within the density functional theory as such to compute the band structure and density of states. The gap (G25’‐L1) is indirect gap exhibited as semiconductor, 0.67 eV for the Ge crystal and it is found to be more metallic as intensity of occupied state is increased with Ga doping. The structure Ge:Ga changes during the doping appears to have different bands of energy and thus the energy gap at Fermi energy is also different. The bands are also quantitatively increased. In what we compared at ambient Fermi energy it is shown that the valence band is shifted to the higher positive value of energy bands when Ga atom concentration is increased. The density of states value at Fermi energy is also increased while the binding energy is decreased.