Structure Optimization Of Silicon Drift Detector And Performance Research Of Nettype Small Pixel Detector

Silicon semiconductor detectors are widely used in various fields such as aerospace and medicine due to their excellent physical properties.This paper mainly studies the silicon drift detector(SDD)used in the aerospace field and the mesh-type small pixel silicon detector used in the medical field,and optimizes and improves its structure and performance on the basis of the traditional structure.Since the SDD is laterally depleted,the electric field for transporting electrons is independent of the depletion electric field.This transportation method can make the effective area of the collecting electrode independent of the cell area of the SDD,and the capacitance of the SDD is not affected by the cell area of the SDD.SDD is mainly used in the aerospace field and requires an array with an area of about(2000-10000 cm~2).If a small area SDD unit is used to form a large SDD array,the production cost will increase,the technical difficulty will increase,It also reduces the effective area of the detector in the array。so the development of large-area SDD is imminent.1.This paper designs the SDD with a voltage divider resistor chain and floating electrodes.This structure is optimized on the basis of the traditional concentric ring SDD structure.Using atomic layer deposition technology to deposit a layer of voltage divider resistance chain between the cathode rings of the concentric ring SDD(above the silicon dioxide),which solves the disadvantage that the concentric ring SDD requires an external voltage divider.A floating electrode with the same doping concentration as the cathode ring is injected between the cathode rings(below the silicon dioxide)to achieve the purpose of reducing leakage current,uniform electric field and improving device performance.2.The mathematical variational method is used to calculate the best drift trajectory of electrons drifting to the collecting electrode.A single-sided concentric ring SDD with a radius of 1560μm was designed,and the electric field,potential,electron concentration and leakage current of floating electrode structures of different numbers and sizes were simulated and compared.When four groups of floating electrodes are added,it has the best electron drift channel,and the leakage current is 3orders of magnitude smaller than that of the structure without floating electrodes.In this paper,a single-sided concentric ring SDD with a radius of 4040μm is designed.Simulations show that as the radius increases,the drift track gradually approaches the bottom surface.If the radius increases again,breakdown occurs on the bottom surface.The area of a single-sided concentric ring SDD cannot be too large.Therefore,a double-sided concentric ring SDD with radii of 10080μm and 20130μm was designed.3.This paper also designs a network-type small pixel detector for medical detection direction.By designing the shape of the collecting electrode,the effective area of the collecting electrode is reduced,and the purpose of reducing the capacitance and improving the performance of the detector is achieved.In this paper,the mesh structures with electrode shapes 2×2(hereinafter referred to as n=2)and3×3(hereinafter referred to as n=3)are designed respectively.This paper compares the full depletion voltage,potential,electric field,electron concentration,capacitance and leakage current of the two structures with n=2 and n=3 under different electrode widths.It is concluded that when n=3,the electrode width is 5μm The current structure meets the design requirements.