Optimization Of The Enhancement Of The Si-based APD For Near-ultraviolet Detection Through Structural Design

The silicon avalanche photodiode(Si-APD) is widely used for its high-gain, low noise, fast response in the optical detection field. But with the rapid development of near-ultraviolet astronomy and meteorology, near-ultraviolet communications and missile guidance and other aspects, being not sensitive enough in the Near-ultraviolet region has restricted its development in the near-ultraviolet detection field.In this paper, we will investigate the factor that affects Si-APD’s near-ultraviolet responsiveness in two aspects: one is the doped distribution of the APD layered structure and another is the system of membrane on the surface.As for the APD layered structure, we use the absorbed field-controlled multiplied separation(SACM) structure as a model, deduced the distribution of electric field in each layer and got the relationship between electric field and gain factor as well as that between electric field and the breakdown voltage. Then we explored the microscopic behavior that the incident photon generates avalanche current, and got a conclusion that the thickness of non-light-sensitive layer makes an effect on the near-ultraviolet detection sensitivity. Then we get the layers’ contribution to the quantum efficiency that were calculated by layered way. Also in this paper we derivative the satisfied condition of the AR coating by Fresnel principle and propose innovatively high and low refractive index multi-layers arranged in alternating on the Si-APD surface, which achieve the purpose of optical frequency selection and ensure the high transmission at the same time. Then we got the optimal doping profile with the quantum efficiency of 35.0% at 400 nm calculated by Matlab.Finally, we established the structure model by Silvaco, obtained the structure of approximate optimization model by optimizing technological process, simulated the optimized structure and obtained the detection sensitivity of 250 A/W(406 nm), which is 12.2 times of the detection sensitivity of 18.9 A/W of the initial structure, and got the detection sensitivity of 80.3 A/W(405 nm) by experiment, which further confirmed the feasibility of the optimization program.