Energy Transport Of GaN-¹⁴⁷Pm Beta Voltaic Nuclear Battery And Optimization Design Of The Battery

The interaction between electron and semiconductor material is thefoundation for the β-voltaic nuclear battery. Electron-hole pairs will createdirectional drift current forced by built-in electric field. The β-voltaic nuclearbattery has been extensively set under the spotlight because of its severaladvantages, such as Long life, small size, stable output, high energy density.The nuclear battery in my work used pure¹⁴⁷Pm Radioactive sources and GaNmaterial which is the three generations of semiconductor materials. This workemployed the Monte Carlo method to simulate the energy transportation inGaN and self-absorption of¹⁴⁷Pm concluding some reasonable results.my research include five parts as below:1.got the relationship between the1/10or1/100Range of electron andthe single-energy of electron. I simulated the curve of this relationship usingthe experience formula getting perfect results. The result would be helpful forthe design of the depth of depletion region and protective material.2.got the relationship between the energy backscattering ratio（η） and theenergy of electron（E）、the injection angle（θ）.The curve ofη-θ was simulatedperfectly by Origin8.0in the condition of the electron of the energy of60keVdirectly. The energy scattering ratio increases with the injection angle and theincreasing rate also increases with the injection angle. The energy scatteringratio is not very high while the injection angle is from0°to20°. Based on theresult I researched，I gave two optimal reasonable designs. We could drawsome conclusions:1)There is not strong relationship between the energyscattering ratio and the energy of electron while the injection-energy ofelectron is from5keV to400keV.2)The energy scattering ratio in4π is higherthan in DIR, while the energy of electron and the target material are same3)The energy scattering ratio increases with the density of device material while the energy of electron, the target material and the way（4π or DIR） areall the same.3.I researched the law of self-absorption of¹⁴⁷Pm.1)The relationshipsbetween the surface radioactive activity and the mass thickness indicates thatthe surface radioactive activity would increase dramatically with the massthickness at first, and then the increasing rate decreased and finally thesurface radioactive activity reach the highest point at certain massthickness.2)I also researched the dependence of surface power of radioactiveresource on mass thickness. And I draw the conclusion that the surface powerwould increase dramatically with the mass thickness at first, and then theincreasing rate decreased and finally the surface power reach the highest pointat certain mass thickness.3)the dependence of the energy spectra of βparticle emitted from the source surface on mass thickness.4)I plot the curveof the self-absorption of¹⁴⁷Pm of different mass thickness which was simulatedperfectly by Origin8.0. Considering reducing the self-absorption of radioactiveresource and improving the surface output power, we give the optimalradioactive resource of¹⁴⁷Pm. The characters of this kind of resource are setas below: mass thickness is7.53mg/cm^2; total radioactive activity is7Ci; thesurface radioactive activity is3.19Ci; surface power is1557.56μ w/cm^2;self-absorption is about54.47%.4.The relationship between the energy deposition ratio and the depth inGaN material for single-energy electron or the radioactive¹⁴⁷Pm resourceindicates that1)there is a main energy deposition region. The depositedenergy rate is a function of the depth in GaN. The deposited energy increasesfirstly and then decrease with the depth of GaN material after reaching thehighest point.2)The higher the energy of electron, the deeper the maindeposited region is.3)when we use the radioactive¹⁴⁷Pm resource, we drawconclusion that the energy deposition rate decreases as the energy of electronincreasing. The optimal width of depletion layer is about35μ m. 5.Optimization and Design:（1）The depth of PIN junction is0.3μ m;Doping concentration（N_A） of the P⁺is2.2E19cm^-3; Doping concentration（ND） ofthe N is2.63E12cm^-3; Doping concentration of the N⁺is5E18cm^-3（.2）Dependon the characters we mentioned above, I calculated the nuclear batteryperformance. The short-circuit current(I_SC) is13.66μ A; The open circuitvoltage(V_OC) is3.127V;The maximum output power（Pm） is40.68μ W; Energyconversion rate（η） is5.22%（.3）Improved design: Series or parallel of nuclearbattery and the design of electrode.