Investigation On Effect And Laser Annealing Treatment Of Implanted 6H-SiC Irradiated By Nitrogen Ions

Silicon carbide is a third-generation semiconductor with excellent properties such as irradiation resistance,high temperature resistance and high thermal conductivity.It is widely used in irradiation environments such as aerospace electronic components and nuclear protection.Space irradiation causes damage to electronics,where the material damage is the key roblem.So far,the irradiation damage of SiC materials is not sufficient,Therefore,it is very meaningful to study the irradiation effect of SiC materials and the annealing recovery after irradiation.In this paper,6H-SiC semiconductor materials were used as the research object.The effects of 150 keV nitrogen ion irradiation on the microstructure and photoelectric properties of the materials were studied by means of Raman spectroscopy,X-ray photoelectron spectroscopy and ultraviolet-visible spectrophotometer.Meanwhile,it is of importance to find the suitable laser annealing treatment to restore the lattice structureThe 6H-SiC crystal wafer turns from dark green to black in color and the visible light transmittance of the sample is significantly decreased after it is irradiated by nitrogen ions.The characteristic Raman peak of SiC is significantly decreased and a new Raman peak appears after nitrogen ions irradiation.XPS analysis shows that C content of the irradiated surface layer increases significantly while the Si content decreases instead.At the same time,Si-C bond peak position shifts significantly.In order to recover the lattice structure,the irradiated 6H-SiC sample is treated by laser annealing at three different energy densities(0.6 J/cm~2,0.8 J/cm~2,and 1.0 J/cm~2).When the energy density is 0.6J/cm~2,the recovery degree of the damaged crystal is about 20%.When the energy density is up to 0.8 J/cm~2,the recovery degree of the damaged crystal is nearly 90%.If the energy density reaches 1.0 J/cm~2,ablation holes appears on the surface of the irradiated 6H-SiC and the degree of damage is increased.Results show that the nitrogen ions irradiation can induce preferential sputtering of Si and the C enrichment in the surface layer of 6H-SiC sample.And the irradiation can also lead to amorphization of the 6H-SiC sample.Nitrogen ions implantation introduces a large number of defects to the 6H-SiC sample and induces a decrease in the transmittance of the sample and a significant increase in the absorption coefficient,which is ascribled to a reduction in the optical band gap from 3.02 eV to 1.12 eV.Among the three laser energy densities,the laser annealing with 0.8 J/cm~2 can restore the crystal lattice of irradiated sample with ideal effect.