CMOS photodiode with enhanced responsivity for the UV/blue spectral range

A new photodiode for the UV/blue spectral range, which can be integrated monolithically with CMOS circuits, is presented. Such optoelectronic integrated circuits (OEICs) with a high sensitivity in the UV/blue spectral range are needed in near-future optical storage systems like digital versatile disk (DVD) or digital video recording (DVR). At 400 nm, our so-called finger photodiode achieves a responsivity of 0.23 A/W corresponding to a quantum efficiency η of 70% [with an antireflection coating (ARC)] and rise and fall times of 1.0 ns and 1.1 ns, respectively. The finger photodiode can be used in the red spectral range, too. At 638 nm, the responsivity is 0.49 A/W (η=95%) and rise and fall times of less than 2.3 ns are achieved. For the integration of the finger photodiode in an industrial 1 μm twin-well CMOS process, only one additional mask is needed in order to block out the threshold voltage implantation in the photo-active region