Gigabit photodiodes in standard digital nanometer CMOS technologies

A study of the performance of photodiodes in a fully standard sub 0.1 /spl mu/m technology is presented. A one-dimensional model is developed to get a rough idea of speed and responsivity of the detectors. Next, two-dimensional simulations of two basic unit cells are performed The importance of the side-wall capacitance of a junction is demonstrated, and a clear trade-off between speed and responsivity is shown. According to simulations, the nwell diode can achieve a bitrate of 200 Mbit/s and a responsivity of 0.36 A/W. By considering also the p/sup +/ to nwell junction, a bitrate of 1 Gbit/s and a responsivity of 0.08 A/W can be achieved. Finally, the layout issues of different test diodes are discussed.