Study On Electrical Characteristics Of Low Deadzone Composite Shell-Electrode Silicon Detector

While semiconductor materials and fabrication technologies have been developing rapidly,the traditional detector technology has become more increasingly sophisticated,and new material semiconductor detectors have also increasingly come into sight.As an typical kind of semiconductors,silicon detectors,which are advanced in Si processing technologies,have been applied in many fields,such as high energy physics,photon science,etc.This kind of detectors have been widely used especially in high energy physics because of their outstanding radiation hardness.Despite that,when detectors are implemented in LHC(Europe's Large Hadron Collider)experiments,the performance of detector will be influenced while total radiation fluence is up to 1×1016n/cm2(1 MeV neutron equivalent).Usually,detector electrical properties are degraded.These degradation's are increase in leakage current,increase in capacitance under a given voltage,increase in depletion voltage,decrease in charge collection,increase in response time.They will also impact the detector performance parameters such as noise,energy consumption,and energy resolution.To the detector radiation hardness,a novel Low Dead-zone Composite Shell-electrode Detector(LDCD)has been proposed in this thesis.In this novel structure' detector's low electric field area is eliminated and the detector's charge collection efficiency is improved.LDCD is simulated with a simple square structure by using the Silvaco TCAD to study various properties of the detector.Simulation results are analyzed and compared to the theoretical calculations.Combined results of simulations and calculations are used to determine the electrical properties of the LDCD.The conclusions are listed as follows:(1)Detailed description of the novel LDCD concept and designing.This design is a quadrangular prism nested bottom special structure modified to double-sided etching,improved from the traditional single-sided etched square structure(the bottom short quadruple prism etched away four quarter circles).Therefore,dead space is obviously reduced and resistance to radiation is increased by virtual of this new detector design.(2)Simulation of Electrical Properties of the novel LDCD.Based on the basic theory of semiconductor silicon detectors,combined with simulation results the relationship between the full depletion voltage,leakage current,capacitance and other electrical characteristics of the new structure detector in the radiation environment and the detector's are structure are studied.The full depletion voltage of the novel LDCD with square shape(non-irradiated)is about 1.5 volt.Studies have shown that the effect of irradiation on leakage current is due to the influence of irradiation on the carrier lifetime of the detector material.The value of leakage current is not influenced by the structure's geometry parameter,if the detector volume is not changed.The SNR(Signal to Noise Ratio)is related to the value of the leakage current.In addition,through the simulation of C-V characteristics,it is known that the saturation capacitance of this detector is 87 fF.(3)The LDCD's charge collection efficiency(CCE)is studied.Combining charge-collection theory,a simple charge-collection model is deduced through simulation calculations.The results of the study show that in the non-irradiation environment,the total charge received by the collector electrode is independent of the position of the minimum ionizing particle(MIP)incident.When the device is in a strong radiation environment,charge collection is related to the incident position of the MIP:The higher the radiation intensity,the lower the charge collection efficiency of the new low-dead-zone composite-structure shell-type electrode silicon detector,and the charge collection efficiency is closely related to the size of the electric field.Therefore,the necessary of reducing the deadzone of the detector is proved again.