The grain size dependence of the mobility and lifetime in chemical vapor deposited diamond photoconductive switches

The grain size dependence of the carrier lifetimes and collection distances of chemical vapor deposited (CVD) diamond films of 0.1-10 mu m average grain size was measured. The estimated values of the mobilities and lifetimes indicated that the dominant recombination process had occurred inside the grains, not the grain boundaries. This finding was confirmed by measuring the electric field dependence of the lifetime and the collection distance. Under a high electric field, however, a major decrease in decay time is expected for smaller grain sizes, due to the increase in the number of carriers which reach the grain boundaries during their lifetime. Such a decrease was observed in a 0.8-mu m grain size sample at E=10(5) V/cm. The data also showed that a 1-ps kV electrical pulse from a dc bias across a diamond film coated gap can be achieved with a CVD-deposited diamond photoconductive switch of sub-mu m grain size. (C) 1998 American Institute of Physics. [S0021-8979(98)02503-1].