Determination of trapped charge emission rates from nonexponential capacitance transients due to high trap densities in semiconductors

Simple analytical expressions are derived to determine the trapped charge emission rates from the initial or final decay of capacitance transients in a semiconductor junction containing shallow dopants and traps of arbitrary profiles, even though the whole decay is nonexponential due to high trap densities. Two special cases of density profiles are then examined. ‘‘Nonexponentiality’’ is quantitatively defined and simple expressions are presented. We show that charging traps in part of the depletion layer may increase or reduce nonexponentiality, depending on the trap density in the region dynamically swept through during the transient. Measurements on a gold-doped diode give good agreeement with our analysis.