A novel photoconductive detector for single photon detection

We report on first results of an ultra sensititve photo-conducting detector. It basically represents a p–i–n diode and junction FET integrated into a single device. The extremely high detectivity can be achieved by reducing the electrically active area and hence, the capacitance of a p–i–n photo-conductive detector without reducing the optical area. For this purpose, we have fabricated p–i–n-structures consisting of crossed p- and n-doped stripes of a few micrometer width. While the top n-stripe can easily be defined by wet-chemical etching, focussed Be ion beam implantation is used to define a buried p-doped stripe in a GaAs wafer. We show that room temperature dark currents at a few volts reverse bias are in the low pA- and capacitances in the low fF-range and the expected large photo-conductive gain is observed.