Anomalous electrical conduction in silicon resistors at low temperatures

Charge transport phenomena in highly compensated Si resistors have been investigated in the temperature range 4.2 - 300 K from measurements of the I - V static characteristics. The prebreakdown and breakdown regions of I - V characteristics, observed at liquid-helium temperatures, were simulated by a one-dimensional model including the high compensation effect as well as the impact ionization of the frozen-out shallow dopants by the hot electrons injected into the base. An impurity hopping conduction mechanism is considered for the prebreakdown regime at temperatures between 4.2 and 20 K. Negative differential resistance (S-type) phenomena are also observed on the I - V characteristics for high injection current densities and are discussed in terms of the inhomogeneous distribution of the electric field into the base at liquid-helium temperatures.