| Avalanche photodiode (APD) is widely used in the field of photoelectricdetection by people of all ages with its internal gain characteristics. the APD nowhas the PIN, SAM, of SACM and RCE and other structure after years ofdevelopment. Device performance is improving constantly. Compared with otherdirect band gap materials, Si material has much lower inter-band tunneling current,which makes a better noise performance of Si-based APD. Since APD array devicehas been made by MIT in1998, the demands to increasing the gain and reducing theperformance of avalanche voltage of array elements become a research hotspot. Astechnology advances, the order of magnitude of APD micro-nano manufacturing ispossible. The study of high-gain and low operating voltage APD has become anurgent requirement in the field of array integration.In this paper, we analyze the avalanche gain and structural parameteroptimization of silicon-based SACM-MAPD(Separated Absorption, Charge, andMultiplication Micro-pixel Avalanche Photodiode). First of all, according to theimpact ionization theory, Monte Carlo method is used to build a Si material impactionization model and then the curve of the ionization coefficient and electric fieldstrength in the Si material is given. Secondly, Monte Carlo method is used to build aSi SACM-MAPD model, concerning the influence of different thicknesses anddoping concentration of the charge layer on the avalanche gain, response speed,spectrum response, the device structure parameters were optimized by using it. Atlast, the fabrication process and electric properties simulation of the device is madeby a computer-aided design software, Silvaco TCAD. We get the fabrication processconditions of the high gain MAPD，and the breakdown voltage and avalanche gainfactor are simulated. As a very important fabrication process, the secondaryinjection impact on device avalanche gain performance has simulated at the sametime, the results shows consistency with MC simulation. |
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