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 dist ances of chemical vapor deposited (CVD) diamond films of 0.1-10 mu m a verage grain size was measured. The estimated values of the mobilities and lifetimes indicated that the dominant recombination process had o ccurred inside the grains, not the grain boundaries. This finding was confirmed by measuring the electric field dependence of the lifetime a nd the collection distance. Under a high electric field, however, a ma jor decrease in decay time is expected for smaller grain sizes, due to the increase in the number of carriers which reach the grain boundari es during their lifetime. Such a decrease was observed in a 0.8-mu m g rain 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 b e achieved with a CVD-deposited diamond photoconductive switch of sub- mu m grain size. (C) 1998 American Institute of Physics. [S0021-8979(9 8)02503-1].