Current Flow across Grain Boundaries inn-Type Germanium. I

A theory of the current flow across grain boundaries in n-type germanium is given. In the temperature range where carrier generation in the space charge region can be neglected and for donor concentrations in the bulk larger than 1014/cm3, the current is carried essentially by electrons crossing the barrier, the zero bias conductance is independent of the donor concentration and is given by G0=2.2·108Te−φ0/kT. The apparent activation energy φ0 is directly related to the barrier height. The current for applied voltages which are large compared to kT/q fails to saturate. The deviation for saturation is related to the density of states in the boundary band. At sufficiently low temperatures the carrier generation in the space-charge region is the rate-determining process for the current flow across the boundary.