Fabrication And Properties Of GaN-based Neutron Detector

Neutrons are uncharged and are not obstructed by the coulomb forces when they interact with the nuclei.Advanced neutron detection technology is the basis for conducting precision neutron physics experiments and plays an important role in the fields of nuclear reactors,new energy technologies,nuclear weapons research and design.The neutron detector for neutron detection technology is the most front-end devices and one of the most critical components.The first generation of 6Li sandwich semiconductor silicon neutron detector based on nuclear reaction method has the advantages of low power cons?mption,wide linear response range,fast response time,good n/y resolution,small vol?me and low working voltage.Many applications replace 3He proportional counters,BF3 proportional counters and scintillation detectors.However,in the fields of neutron logging,oil and gas exploration,underground prospecting and radioactive detection of nuclear power stations,neutron detectors are exposed to harsh working environments with high temperature or strong radiation.Therefore,these applications have proposed new performance requirements for semiconductor neutron detectors.Based on the third generation of wide bandgap galli?m nitride materials with excellent properties of large forbidden band width,high threshold potential,high breakdown electric field,high electron saturation rate,high thermal conductivity,high breakdown electric field and good chemical stability,The neutron detector based on GaN-based neutron detector has the advantages of high radiation resistance,high temperature resistance,wide linear response range,fast response time,good n/y resolution,small volume and low working voltage.It is suitable for neutron detection It has good application prospects.In this paper,based on the interaction between neutron and GaN and the detection mechanism,the GaN-based neutron detector is designed and prepared around the preparation process of GaN devices and the properties and characteristics of the neutron conversion layer.This paper mainly carried out the following research contents and results:(1)Using SRIM and MCNP to simulate the impact of alpha particles in GaN materials on the range,charge transport characteristics,and device structure on the charge collection efficiency,a simulation model of alpha particle detector was established,and different thicknesses of 6LiF were simulated.The effect of the conversion layer on neutron conversion efficiency.According to the results of theoretical simulation analysis,the device structure of the detector is designed.A GaN-based pin structure was epitaxially grown on a sapphire substrate by MOCVD method.The ohmic contact and Schottky contact of n-and p-type GaN were discussed.The influence of the interface state on the ohmic contact and the Schottky contact was analyzed.As a result,a pin structure alpha particle detector was prepared.According to the prepared pin detector,the electrical properties of the detector were tested,including I-V and C-V.Using the 241 Am source,the charge collection efficiency and alpha energy spectrum of the device under different voltages and different areas were tested.The test results show that due to the strong polarization effect of GaN,when the bias voltage is OV,the detector has the smallest leakage current and the best spectral resolution.(2)GaN is a third-generation wide bandgap and straight-gap semiconductor material.Its main advantages in nuclear radiation detection are high temperature resistance and radiation resistance.This article has conducted high-temperature testing of GaN-based pin detectors,with test temperatures ranging from 290 K to 475 K.The test results show that when the temperature rises to 475 K,the FWHM of the detector changes very little.This shows that GaN-based nuclear radiation detectors can work in environments above 475 K.In this paper,the experimental study on the effect of high energy 10 MeV electron irradiation on the performance of GaN-based pin alpha particle detectors is also carried out.Using different injection doses of electrons,the detector's electrical properties,alpha particle energy spectrum and other characteristics were tested and analyzed in detail.The results show that when the implantation dose is greater than 100 KGy,the performance of the device begins to deteriorate,and the charge collection efficiency begins to deteriorate.(3)Based on the principle of neutron detection by nuclear reaction method,the key material 6LiF of the neutron conversion layer was simulated to simulate the influence of different thicknesses on the neutron conversion efficiency;combined with the difficulty of the film preparation method of the current conversion layer,the focus was on the development of heat.The preparation of 6LiF thin film by evaporation and sol method was studied.The preparation methods under different process conditions were discussed in terms of surface morphology,crystal quality and film growth rate.The results of the study show that the process is simple and the prepared film has good performance.Combining the prepared 6LiF neutron conversion layer,a fast neutron measurement experiment of GaN-based pin neutron detector was performed using 241Am-Be fast neutron source,and high-density polyethylene was used to convert fast neutrons into heat.Son,using pulse counting,neutron detection.The experimental results show that when the thickness of 6LiF is 16.9?m,the thickness of polyethylene is 7mm,and the reverse bias is-10V,the neutron detection efficiency of the detector is 1.7%.Through the theoretical analysis of GaN-based neutron detectors,simulation simulation,device structure design,epitaxial growth and characterization,alpha particle detection performance,high temperature and radiation resistance test,6LiF preparation and fast neutron detection performance and other key issues Targeted research.The application of GaN-based nuclear radiation detectors has been expanded.For the first time,a 6LiF-based GaN-based neutron detector has been successfully fabricated.Based on the above research work,it has been proved that GaN materials have advantages of high temperature resistance and radiation resistance as nuclear radiation detectors,and the application of GaN-based nuclear radiation detectors in industry can be carried out.