Silicon p-n junction photodiodes sensitive to ultraviolet radiation

Experimental studies on a silicon photodiode have been carried out to achieve the performance characteristics required for applications such as spectroscopic measurements. Sheet resistance was applied as a control parameter for diffusion to obtain a shallow junction less than 1 µm in depth. For high ultraviolet responsivity, the diffusion layer, in which a built-in field is induced by the impurity gradient, was optimized for values of the sheet resistance of about 800-2000 Ω/□. The device responded in the wavelength range of 200-1000 nm,and had a responsivity of 0.065 A/W at 200 nm. In order to reduce influence of stray light in spectroscopic measurements, two types of photodiodes were fabricated with photoresponse reduced in the long-wavelength portion. A p⁺-n-p⁺device was found preferable to a p⁺-n-n⁺device. And the device structure with an extended electrode was desirable for high, reliable performance.