PHOTODIODES WITH PHOTOCONDUCTIVE GAIN ENHANCEMENT

摘要

The present invention provides photodiodes exhibiting photoconductive gain. It is shown that photodiodes may exhibit photoconductive gain under certain conditions, and traditional photoconductive gain theory has been extended to describe these cases. Particularly, there is introduced the basic principles of photoconductive gain in p-i-n diodes, and there is described several approaches to designing photodiodes with photoconductive gain. In one approach, photogenerated carrier delay is used to obtain photoconductive gain in a photodiode. Delay structures inserted into the intrinsic region preferentially impede the flow of one of the carriers relative to the other to obtain the gain. Another method of obtaining photoconductive gain in a photodiode is to increase the rate at which electron-hole pairs are generated in the p-region or n-region, so as to decrease the times τp or τn. One way of decreasing τp or τn is to include a region of 'ultra-fast' high B-coefficient material in or near either the p-region or n-region, which has a much lower value of τp or τn for a given doping level.