Study On Electrical Properties And Its Annealing Behavior For Neutron Irradiated6H-SIC Crystal

SiC is an important irradiation resistance material, which has attracted more andmore attentions due to its many excellent characteristics. As a structural functionalmaterial, SiC composite material is a kind of great potential application in fusionreactor facing plasma component preparation. In the process of the application, theion irradiation can produce a large number of defects that lead to the electrical, optical,thermal and mechanical properties degenerated. Moreover, the feasibility andreliability of SiC are directly determined by degradation degree. Therefore, fullunderstanding the formation mechanism of irradiation defects, micro-architecture andthe effect on the macroscopic properties is very important. On the basis of the Halltesting method, we tested and calculated the carrier concentration and mobility of then-type6H-SiC doped with nitrogen single crystal. The effects of the annealing on theelectrical properties of the irradiated6H-SiC single crystal were studied through nocontact resistance test methods and LCR dielectric properties analysis.1. Large doses of neutron irradiation generated a large number of defects andinjuries in the crystal and caused the changes of the electrical properties of the sample,which lead to the higher resistivity, smaller dielectric constant and dielectric loss.Finally, the semiconductor characteristics of the samples were destroyed. A largenumber of deep level defects existed in the crystal after neutron irradiation. Thesedefects captured many carriers so that the resistivity increased. Furthermore, thedefects captured charges forming space charge,and then affected the dielectricproperties.2. We found that there were two characteristic temperatures during the process ofthe defects evolution and the recovery of the electrical properties, i.e.,1000℃and1400℃. At the annealing temperature of <1000℃, the resistivity of irradiatedsample slightly increases, while the dielectric constant and the dielectric loss decreasewith the increase of annealing temperature. At the annealing temperature of>1000℃, the resistivity decreases gradually. But the dielectric constant and the dielectricloss increase at the annealing temperature of>1400℃.3. When the fluence is not higher than about1022n/cm2，The defects exist in theform of Si interstitial Sii, C interstitial Ci,Carbon vacancies VCand silicon vacancies VSiin neutron-irradiated nitrogen-doped silicon carbide crystals. At the annealingtemperature of <1000℃, Si interstitial Siiand C interstitial Cimigrate. When theannealing temperature is between1000℃to1400℃,vacancies can migrate，recombinant and annihilate. When the annealing temperature is more than1400℃，these defects induced by irradiation eliminate or achieve a sense of stability. Theproduct of transmutation15P begins to release electrons.