Equivalent circuit modelling of p-i-n photodiodes for 40 Gb/s receivers

We have described a back-illuminated photodetector with an 0.62 A/W responsivity, a typical dark current of 3 nA at -5 V bias, a failure rate of less than 1 FIT at 40°C, and a bandwidth (into a 50 ohm load) as high as 39 GHz. By inserting a tunnelling element into an otherwise standard equivalent circuit model, we have shown that this model is capable of self-consistently fitting photodiode S-parameter data and explaining a broad range of behavior including low frequency tailing. The physically-based equivalent circuit model and parameter extraction allows an understanding of detector performance and improved control of device processing. The detector is suitable for operation in 40 Gb/s receivers.