| The frequency response characteristic of photo-current of traditional avalanche photodiode is analyzed in this paper. The structure of avalanche photodiode which is designed considering to dark current and frequency response is improved. This improvement not only increases the characteristic of dark current and frequency response, but also suppresses edge pre-breakdown completely, and promises 2V of increasing of breakdown voltage and multiplication gain at 8.Electronic-hole pairs are generated in absorption layer when light is shining down upon avalanche photodiode, according to photoelectric effect. When Electronic-hole pairs are driven into multiplication layer, Avalanche effect is triggered, photo-current is formed. This paper mainly analyses InGaAs/InP avalanche photodiode with sagcm structure. According to the existing equivalent circuit model influence on frequency response from different thicknesses and doping of avalanche photodiode is simulated using ADS, and so is positive illuminating and back illuminating. Then several structures that can be used to suppress pre-breakdown of avalanche photodiode are discussed. The electric field distribution in APD is calculated according to Poisson equation, and simulated using matlab. On the basis of simulation result, a new structure is given out. It can be seen that APD with new structure is not only harmless to bandwidth, but also suppresses the edge pre-breakdown according to the simulation. And the process of new structure is simpler than traditional APD. At last, the sensitivity of APD with a simple detector circuit is calculated according to sensitivity equations. |
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