Field-enhanced carrier generation in MOS capacitors

When sufficiently high voltage steps are used for driving a metal-oxide-semiconductor capacitor (MOSC) towards deep inversion, the temporal evolution of the current and of the high-frequency capacitance during the return to equilibrium cannot be interpreted on the basis of a theory assuming a constant bulk generation lifetime. A more general theory, which takes into account field-dependent carrier emission rates, is developed and it is shown how current and h.f. capacitance measurements can be used to determine the field dependence of the bulk generation lifetime. The results of experiments performed on differently processed MOSC's are presented; they support the hypothesis that field-enhancement of carrier emission rates takes place according to a mechanism of the Poole-Frenkel-type.