The Study On Suppression Of Edge Pre-breakdown And Excess Noise Factor Measurement Of APDs

There continues to be a strong interest in the use of avalanche photodiodes(APDs) in the field of quantum key distribution, national defense, astrosurveillance and other photon starved optical communication because of their high sensitivity and high multiplication gain. The application development of APD is limited by the shot noise, and the main influence factors are dark current and excess noise. We respectively studied the dark current through simulation and tested the excess noise factor, which has guiding signification for the development of the high speed and low noise APD.Firstly, the influence of electric field distribution on dark current of APD was studied. In order to solve the edge breakdown of planar InGaAs/InP APD which has been widely used, we studied the deep guard ring method that had been existed to suppress pre-breakdown by means of simulating electric field distribution of different structures with COMSOL semiconductor module. In addition, as the advantage of the deep guard ring, it will be applied to the vertical incident planar Si/Ge APD, thus reducing the tunneling current of the Ge absorption layer.Then in order to study the excess noise characteristic, two improved APD excess noise factor test system respectively based on noise figure meter and lock-in amplifier were set up to test the noise of the same APD. The problems that the two kinds of test schemes existed were analyzed by compared with experimental data. We studied the impact of the relative intensity noise of the laser on the excess noise test, and proposed the corresponding processing scheme. Finally a new test scheme based on balance detection which can eliminate the noise of light source was put forward, and the existing problems and the feasible solutions were analyzed and studied theoretically.