A simple technique for determining deep-level concentrations in high-resistivity semiconductors using capacitance transients

Many of the practical difficulties of using capacitance transient techniques to determine the concentration of deep levels in the depletion region of a semiconductor diode are discussed with particular reference to high-purity germanium. A method called the ΔV_C /V_P technique, is shown to have many advantages for high-resistivity materials when the deep-level concentration is relatively large (N_T/N_B⩾0.01) and particularly when there are temperature-dependent equivalent-circuit effects. The technique involves matching the capacitances of two different transients, both following pulses of magnitude V_P but with quiescent biases differing by ΔV_C, so that the final value of the capacitance transient with reverse bias V_R+ΔV_C is the same as the initial value of the transient when the reverse bias is only V_R. The ratio of deep levels (causing the transient) to shallower levels is then given by ΔV_C/V_P