The Study Of Structural Optimization On Reducing The Dark Current Of Si-based Micro-pixel Array APD

Micro-pixel array Si-APD, with its advantage of high gain, fast response, highsensitivity, wide dynamic range, not sensitive to magnetic fields, etc, has beenresearch focus of single-photon detectors in recent years. But dark current is always amajor factor restricting the detection accuracy of feeble light, which limits itsapplication in many research fields, such as military, medical, biological,communications and so on.We discuss the factors affecting dark current from two factors, the doping profileof the vertical structure and the crosstalk of the horizontal structure.On the vertical structure, firstly, we construct theory structure model of micro-pixelSi-APD with uniform doping in each layer. Then, with the research thought of electricfield distribution, relationship between electric field and ionization rate, multiplicationfactor and dark current，we build a theoretical analysis framework，which provides amethod for dark current research. Secondly, we study the relationship between electricfield and ionization rate with monte carlo simulation method. Then, the micro-pixelSi-APD is optimized (for1064nm) to have an optimal doping distribution which has atypical dark current of14.5nA and a breakdown voltage of100.7V. this come to theconclusion that dark current is mainly generation-recombination current. By reducingthe concentration of field control layer, we can effectively reduce dark current, but toolow concentration will lose the function of adjusting electric field distribution, and willlead to the breakdown voltage too large. Finally, simulating with silvaco, we gain a lowtypical dark current of2.5nA and a low breakdown voltage of100.7V. Simulationshows that suitable passivation layer and coating can reduce dark current and increasesensitivity. with contrast, the simulation and experimental results fit well.On the horizontal structure，this paper effectively reduces light crosstalk andelectrical crosstalk effects between two adjacent micro-pixel Si-APDs through channelwhich sequentially covered with oxide layer andAl layer.