UV-sensitive low dark-count PureB single-photon avalanche diode

A single-photon avalanche diode (SPAD) with high responsivity in the ultraviolet (UV) wavelength range has been fabricated on Si using PureB (Pure Boron) chemical-vapor deposition to create both a nanometer-thin anode junction and robust light entrance window. The device shows high responsivity at the wavelength of 330 nm and 370 nm when operating in Geiger mode. The dark count rates (DCR) can be as low as 5 Hz at room temperature for an active area of 7 μm². An implicit guard ring, using an n-enhancement implantation in the central region of the diode, is applied instead of peripheral diffused p-type guard rings to achieve a high fill-factor.