Determination of surface recombination velocity and bulk lifetime in detector grade silicon and germanium crystals

The utility of a noncontact photoconductive decay (PCD) technique is demonstrated in measuring the bulk lifetime, τ_B, and surface recombination velocity, S, in detector grade silicon and germanium crystals. We show that the simple analytical equations which relate the observed effective lifetimes in PCD transients to τ_B and S have a limited range of applicability. The noncontact PCD technique is used to determine the effect of several surface treatments on the observed effective lifetimes in Si and Ge. A degradation of the effective lifetime in Si is reported as a result of the growth of a thin layer of native oxide at room temperature under atmospheric conditions