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 d emonstrated in measuring the bulk lifetime, tau(B), and surface recomb ination velocity, S, in detector grade silicon and germanium crystals. We show that the simple analytical equations which relate the observe d effective lifetimes in PCD transients to tau(B) and S have a limited range of applicability. The noncontact PCD technique is used to deter mine the effect of several surface treatments on the observed effectiv e lifetimes in Si and Ge. A degradation of the effective lifetime in S i is reported as a result of the growth of a thin layer of native oxid e at room temperature under atmospheric conditions.