Double-drift avalanche photodetectors

A new avalanche photodiode device is proposed that has superior noise and bandwidth performance. This structure incorporates a drift region on both sides of the high field avalanche region. With the proper design, this reduces the capacitance by nearly a factor of two, without degrading the transit-time limited speed. In fact, it is shown that the double-drift structure ran actually improve the intrinsic device speed. It is also shown that for high speed devices in which the layers must be kept thin, it can be advantageous to absorb light on both sides of the avalanche region, in spite of the consequent increase in the excess noise factor