Injection-Level Studies in Neutron-Irradiated Silicon

The dependence of carrier lifetime on excess density was investigated for neutron-irradiated silicon. Five bulk specimens of n-type (1.0 to 55 ohm-cm) and five of p-type material (2.2 to 56 ohm-cm) were employed. In all cases the lifetime was constant at low excess densities, increased to a value several times larger at excess densities near the equilibrium carrier density, and then decreased. An analysis of the data was performed on the basis of recombination at disordered regions. The effective barrier heights associated with disordered regions were small, about 0.05 eV in n-type silicon and about 0.07 eV in p-type material. These values represent a weighted average for those regions participating in recombination and tend to favor low values. Capture probability ratios and other parameters were also obtained.