Study On Electrical Characteristics Of Novel Closed Shell-Electrode Silicon Detector

With the development of the semiconductor materials and fabrication technologies,more and more semiconductor detectors have been studied.Among them,silicon detectors,due to their excellent properties and advances in Si processing technologies,have been applied in many fields,such as high energy physics,nuclear physics,and so on.Especially in high energy physics,silicon detectors have been widely used because of the outstanding radiation hardness.In spite of that,when the detector is working in LHC(Europe's Large Hadron Collider)upgrades environment,the performance of detector will be influenced since the total radiation fluence will be up to.Usually,we correspond detector electrical properties such as leakage current,capacitance,depletion voltage,charge collection,response time to the detector performance parameters such as noise,energy consumption,energy resolution,collection efficiency.For the purpose of reinforcing the detector's anti-radiation resistance,eliminating the detector's low electric field area and improving the detector's charge collection efficiency,a novel Closed Shell-Electrode Detector(CSED)has been proposed in this work.We simulated CSED with a simple square structure using the Silvaco TCAD to study various properties of the detector,compared them with the theoretical calculations,and analyzed simulation results.The work includes:(1)Detailed description of the novel CSED concept and design.The purpose of this novel detector is to obtain a detector with excellent radiation hardness and minimum dead space.This design is nested by two different structures in such way that the low electric field region existed in conventional 3D-Trench-Electrode Detectors is eliminated.Therefore,the dead space is greatly reduced and the charge collection efficiency is improved by virtual of this new detector design.In addition,the electric field distribution along Z axis is more uniform and continuous.(2)Detector's full depletion voltage: The detector full depletion voltage is related to detector's structure and the working environment.The full depletion voltage can be determined by studying detector's hole concentration distribution.When the hole concentration distribution is no longer changing with applied bias voltage,the detector is in the full depletion situation.The full depletion voltage of our novel CSED with square shape(non-irradiated)is about 1 volt.(3)The relationship of the detector leakage current and radiation fluence: In this work,we study the leakage current under the bias voltage.The main influence of the leakage current is the material's carrier lifetime under radiation.The value of leakage current is not influencedby 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.(4)The capacitance property of the detector: Through the study of the C-V characteristics,we know that the detector's capacitance is 87 fF.The capacitance is related to the detector's structure and the design of electrodes but not the radiation intensity.The SNR(Signal to Noise Ratio)is related to the value of the capacitance as well.(5)The induced current and charge collection efficiency(CCE): When a minimum ionizing particle(MIP)is incident to a silicon detector,an induced current and corresponding induced charge can be read out through the the center collection electrode.The total collected charge is not related to the incident position without radiation.However,when it is in heavy radiation circumstance,the incident position can affect the value of the total collected charge.In addition,our simulation results show that the charge collection will decrease with radiation fluence.The detector's geometry decides the detector capacitance and CCE.