Carrier density dependent photoconductivity in diamond

Single-crystal natural diamonds have been intrinsically photoexcited using 2 ps laser pulses. Electron and hole mobilities and decay times are examined as a function of induced carrier density. Two major density dependent effects are observed. First, at high induced carrier densities, a dramatic decrease in the carrier mobility is observed. This is attributed to carrier-carrier scattering between the electrons and the holes. A model describing carrier-carrier scattering in silicon and germanium has been scaled to diamond. Second, the decay time of the electrons decreases as the initially photoexcited density increases. A simple one-level recombination model successfully explains this density dependence. The combination of these two effects results in a minimum in the measured photoconductive decay times.