ENHANCED PHOTODETECTOR

摘要

The present invention includes a photodiode (10) having a first p-type semiconductor layer (14) and an n-type semiconductor layer (18) coupled by a second p-type semiconductor layer (16). The second p-type semiconductor layer (16) has graded doping along the path of the carriers. In particular, the doping is concentration graded from a high value (15) near the anode to a lower p concentration (17) towards the cathode (22). By grading the doping in this way, an increase in absorption is achieved, improving the responsivity of the device. Although this doping increases the capacitance relative to an intrinsic semiconductor of the same thickness, the pseudo electric field that is created by the graded doping gives the electrons a very high velocity which more than compensates for this increased capacitance.