High-speed photodetector

A high speed pin-based photodetector comprises a thin light absorbing layer (102), where the applied electric field is high combined with a drift layer (104) exposed to a significantly lower electric field. Only the charge carriers with the higher mobility will have to travel across the drift layer (104) while the charge carriers with lower mobility will only have to travel over a distance that is less or at most equal to the thickness of the light absorption layer (102). The band gap energy (208) of the drift layer (104) is larger than the band gap energy (206) of the light absorption layer (102). The transition of the higher electric field light absorption layer to the lower electric field drift layer is implemented by the grading layer (105). The reduction of the electric field in the drift layer (104) with respect to the light absorption layer (102) is realized by the distribution of the dopant concentration in the light absorption layer (102), the drift layer (104) and the grading layer (105).