Research On The Deep Level Characteristics Of Semi-insulating 4H-SiC Materials

This Silicon carbide(Si C)material is one of the typical wide bandgap semiconductor materials in the third generation of semiconductor materials.It is widely used in high pressure and anti-irradiation environments and plays an important role in aerospace and other important fields.Due to various reasons such as process and ultra-clean environment,there are N,AI,P and other impurities in the process of growing intrinsic silicon carbide,we call it unintentional doping,and introduce vanadium in 4H-Si C,the donor and acceptor levels can compensate for the above impurity levels and increase the semi-insulation of Si C.Highimpedance semi-insulating silicon carbide can be used to fabricate semi-insulating substrates,power devices,and diodes with excellent performance.However,there are too few reports on deep-level levels in semi-insulating silicon carbide forbidden bands.Deep energy properties have not been fully studied and valued,This paper proposes to explore the deep level information of vanadium-doped 4H-Si C by deep-level transient spectrum test,photoluminescence test and first-principles calculation.The main work is as follows:1.The metallized nickel is plated on both the front and back sides of the Si C sample by magnetron sputtering,and the back contact area is larger than the front surface,and rapidly annealed to form a Schottky contact.The IV test showed that the vanadium-doped 4H-Si C had a high resistance in the dark state.2.Four different bias voltages of 20 V,30 V,40 V and 50 V were selected in the deep level transient spectrum test.The signal peaks near the three temperatures of 260 K,460 K and 520 K were found in the obtained DLTS signal diagram.The News curve analysis obtained the activation energy,the capture cross section and the carrier concentration of the three trap levels.The information data obtained by the analysis is compared with the related paper reports.It is considered that the signal peak near the 260 K temperature belongs to the The Z1/2 level reported in relation to the intrinsic defect of 4H-Si C has been reported,while the signal peak near the temperature of 460 K and 520 K is the same as the vanadium acceptor level already reported in the paper.3.In the photogenerated DLTS test,an acceptor level of 2.286 e V under a conduction band was found,and the emission peak of the same activation energy was also found in the subsequent photoluminescence test spectrum.The domestic and foreign literatures have rarely reported the sub-levels.This level is considered to be the acceptor level introduced by vanadium.4.Photoluminescence test Six emission peaks of 370 nm,410 nm,430 nm,490 nm,540 nm,and 610 nm were found at a normal temperature using a 325 nm He-Cd laser in the wavelength range of 350 to 650 nm,according to the Einstein photon theory.And the energy is transformed,and the energy of these emission peaks is equivalent to the energy level activation energy of the deep level transient spectrum test.5.According to the density functional theory,the first principle study of some properties of vanadium-doped and intrinsic 4H-Si C is carried out.Mainly studied the changes of energy band structure,density of states,density of atomic states and optical properties before and after vanadium doping.The main information obtained is that the doped vanadium atoms introduce a deep level in the forbidden band,and the vanadium doping introduces a dielectric peak into the dielectric function of 4H-Si C,which mainly comes from the forbidden band V to the conduction band Si.the transition of the electrons between the p-states.