Photodetectors with CVD diamond films: electrical and photoelectrical properties photoconductive and photodiode structures

摘要

Free-standing and silicon-supported diamond films have been used to fabricate photoconductiveand photodiode structures for UV light detection. Planar and sandwiched photoconductive structureshave been made on microwave plasma-grown free-standing CVD polycrystalline diamond films of200 μm and 15 μm thicknesses, respectively. A photodiode sandwich structure was obtained onthin (～2 μm) boron-doped diamond films grown on silicon substrate by hot filament CVD.Parameters of defects in the structures were studied by charge-based deep-level transientspectroscopy (Q-DLTS). Planar photoconductive detectors after annealing in air showed a low dark current <10 pA anda high spectral discrimination a l0{sup}4 higher response to 200 nm than to visible (600 nm)wavelengths. The dark current was <10 pA. The turn-off time of the device following exposure tolight was less then 10 ms. It was found that the annealing in air decreases density of point defectsmore than order and strongly increases wavelength discrimination. The sandwich photodiodesshowed a sharp cut-off in photoresponse at 220 nm with a quantum yield of about 0.3 and aphotovoltage in the open circuit regime of up to 1.6 V. Such photodiodes can be used not only for lightdetection but also for light energy transformation into electrical energy as in a photovoltaic cell.