Experimental study of transport in a trap-dominated relaxation semiconductor

The term ``relaxation semiconductor'' has been used to define a category of high-resistivity semiconductors in which the dielectric relaxation time exceeds the recombination lifetime (τD{}τ₀). The transport behavior of semi-insulating GaAs, a trap-dominated relaxation semiconductor, in response to minority-carrier injection has been experimentally investigated. Using a p⁺-{ν}-n⁺ structure, the I-V characteristics have been probed over seven orders of magnitude in current and various regimes have been identified. The experimental results have been compared with previous numerical modeling. A sublinear regime at high bias has been shown to be associated with enhanced trapping by the midgap defects. Impact-ionization processes involving the traps have been demonstrated to be the cause of a sudden rise of current at threshold fields of approximately 1400 V/cm, and the data have been compared to a simple impact-ionization model.