PHOTON NUMBER RESOLVING DETECTOR

摘要

A photon detection system for photon counting comprising an avalanche photo-diode, said avalanche photodiode comprising a p- n junction formed from a first semiconductor layer (103) having a first conductivity type and a second semiconductor layer (107) hav¬ ing a second conductivity type, wherein the first conductivity type is one selected from n-type or p-type and the second conductivity type is different to the first conductivity type and is selected from n- type or p-type, wherein the first semiconductor layer (103) is a doped layer which is doped with dopants of a first conductivity type and where there is a variation in the concentration of dopants of the first conductivity type such that the first layer comprises islands (105) of high field zones surrounded by low field zones, the high and low field zones distributed along the plane of the p-n junction, wherein the dopant concentration is higher in the high field zones than the low field zones, said system further comprising a biasing unit, said biasing unit being configured to apply a voltage which is static in time and a time varying voltage for operating the avalanche photo-diode in gated mode.