Study Of Silicon Carbide Neutron Detectors

Neutron detection technology has a broad application prospect in many fields suchas space radiation environment, contraband detection, national security, basic science,medical and industrial applications. Compared to its counterparts, semiconductornuclear radiation detector has been used more and more widely for the advantages ofmore compact size, simpler structure, higher detection efficiency, larger linear responserange, better energy resolution. However, it cannot be used in high-temperature andharsh radiation environment because of the decreased detection performance. Thisthesis has made some studies on detectors based on wide band gap semiconductormaterial silicon carbide for neutron radiation detection with the purpose of developingnew semiconductor detectors which have higher properties and greater tolerance oftough environment.The feasibility and validity of SiC semiconductor detectors for neutron detectionwere investigated by the methods of combining physical modeling, simulation andexperimental verification.First of all, this thesis established a physical model of PIN type plane neutrondetector based on SiC material, and estimated the sensitive layer thickness, capacitanceand leakage current, the pulse waveform, neutron detection efficiency and intrinsicenergy resolution. The results show that using SiC material as the matrix of neutrondetectors has a good performance in size, time response, neutron detection efficiencyand energy resolution.Then, the relationship between neutron detection efficiency and sensitivity withsensitive volume and polyethylene conversion layer thickness was studied by MonteCarlo simulation method. The results show that, for detectors as small as3mm radiusand30μm depletion layer thickness, detection efficiencies to2.5MeV and14MeVneutron can reach5.71×10-4and2.05×10-3, and respond sensitivity is8.94×10-19C·cm2and5.10×10-18C·cm2respectively. If we add a polyethylene conversion film on the SiCdetector, the response sensitivity can be improved as well as3.8times of the detectorwithout polyethylene conversion film. The research results of energy linear responsecharacteristic show that, detection sensitivity has a good linear proportion relationshipwith the incident neutron energy among the0~14MeV energy range. The responseparameters of the detectors developed in this thesis can satisfy the normal requirementsof neutron radiation detection.Finally, this thesis gave out the method for fabricating a SiC neutron detectorsystem, including SiC epitaxial layer growing methods, ohm contact metal fabrication,electrode structures facture and detector pin package. This thesis also designs thescheme for testing the performance of SiC detector. The test equipment, test process, test methods along with the points for attention were described meticulously in thisthesis, which provide a strong reference to test a nuclear radiation detector of the sametypes.It can be concluded that the SiC film detectors developed in the thesis have highqualities of small size, fast time response, high radiation hardness and temperaturestability, and therefore they can be used as a better alternative detectors in neutrondetection under the high-temperature and high radiation condition.