Study Of Microstructured Neutron Detector Based On 4H-SiC

Neutron detection technique has broad application prospects in the field of homeland security,space science,health care,industry,etc.~3He proportional counter is a kind of neutron detector that most widely used currently.The detection medium ~3He comes mainly from ~3H decay of the nuclear weapons program.With the end of the cold war,~3H reserves reduced which decreased the supply of ~3He,but the demand for ~3He gas all around the world increased greatly,which leads to the serious shortage of ~3He now.So,the research on a new type of thermal neutron detector that can replace ~3He proportional counter has become a hotspot in the world.The microstructured semiconductor neutron detector(MSND)is a new type of neutron detector developed on the basis of the planar semiconductor neutron detector.It can break through the bottleneck of low efficiency of planar neutron detector and has advantages of high energy resolution,fast response time,wide linear range,small size,low power requirement,etc.So the MSND is great alternative of ~3He neutron detector.Traditional semiconductor material MSNDs can work well in common environment,but its efficacy gets worse or even invalid when working under high temperature and strong radiation environment.Compared with the traditional semiconductor material like Si and GaAs,4H-SiC,the third generation semiconductor material,has advantages of large band gap,high critical displacement energy,which can meet the requirement of working under harsh environment.In this paper 4H-SiC is chosen to be substrate material of MSND.Mento-carlo method and TCAD software are used to study thermal neutron detection performance,current pulse response characteristics and charge collection characteristics of MSND.The main research contents and results are as follows.(1)Performance requirements for substrate material and neutron converter material of MSND are summarized.Using 4H-SiC and ~6LiF as substrate material and neutron converter material of MSNDs,respectively,can make MSNDs have advantages of high temperature resistance,radiation resistance,high output signal and great n/?ratio.(2)FLUKA is used to simulate the thermal neutron detection performance of MSNDs with trench patterns,holes patterns and cylinders patterns under different structure parameters and different lower level discriminator(LLD).By comparing thermal neutron detection performance,MSND with trench patterns is determined to own optimal performance.Then,optimal structure parameters of the three basic MSNDs are gotten when LLD is set to300KeV:MSND with trench patterns has the maximum detection efficiency of 30.71%when trench width and distance are 20?m and of 5?m;MSND with holes patterns has the maximum detection efficiency of 30.11%when hole diameter and distance are 30?m and5?m;MSND with cylinders patterns has the maximum detection efficiency of 25.18%when cylinder diameter and distance are 20?m and 10?m.(3)TCAD is used to simulate current pulse response characteristics and charge collection characteristics of?and ~3H of 4H-SiC MSND with trench patterns.The results show that with the increase of the deposition energy of secondary particle in 4H-SiC,current pulse height increases and charge collection time becomes longer.When secondary particles are injected in depletion region,current pulse height is higher,charge collection time is shorter and charge collection efficiency is close to 100%;with the electric field strength of depletion region increasing,current pulse height getting higher and charge collection time becomes shorter.When secondary particles impact outside of depletion region,current pulse height is very small,and the deeper the incident location is,the longer the charge collection time is and the lower the charge collection efficiency becomes.Finally,the production process of4H-SiC MSND with trench patterns is summarized.