Photosensitivity and Noise Characteristic Investigation of Ultrafast InGaAs/InP Avalanche photodetectors

A detailed investigation of photosensitivity and noise characteristics of ultrafast InGaAsP/InP avalanche photodiodes with separate absorption, grading, charge and multiplication regions was carried out. Carrier multiplication and noise factors are evaluated. It is shown that for these purposes input light beam should be well focused to the active photodiode area since peripheral area is quite sensitive to the infrared radiation, too. Noise characteristics reveal the clear fundamental physical processes in avalanche photodiode structure, and also indicate the presence and appearance of defects in the devices.