Compensation Dependence of Impurity Conduction in Antimony-Doped Germanium

A study has been made of the compensation dependence of impurity conduction in n-type germanium containing between 7×{}10¹⁵ and 2×{}10¹⁷ antimony atoms cm^-3, the compensation being changed by fastneutron irradiation. Activation energies ε₁, ε₂, and ε₃, characteristic of the resistivity-temperature curves, change continuously with increasing compensation. The energies ε₁ and ε₂ increase monotonically with compensation, while ε₃ passes through a minimum value. The compensation dependence of ε₂ is in qualitative agreement with the suggestions that this activation energy is associated with the thermal excitation of electrons from the donor ground state to a band that arises from the interaction of negatively charged donors. For small donor concentrations, the value of the compensation at which ε₃ is a minimum is 0.5, in agreement with the Miller-Abrahams theory. At higher donor concentrations, this minimum occurs at smaller compensations. It is suggested that this occurs because the effective compensation at low temperatures is greater than that determined at room temperature, the increase arising because electrons on neutral donors are lost not only to acceptor sites but also to the negatively charged donor band.