Effects Of Rapid Thermal Annealing On W/C Laminated Structures/4H-SiC Schottky Contact And Ultraviolet Detection Properties

SiC is the third generation of semiconductor materials,with a wide band,high breakdown electric field,high thermal conductivity and other advantages,and has a good prospects application in high-temperature and high-power,photoelectric devices.Schottky contact is formed by the contact between metal and semiconductor,which is one of the most fundamental and important structures in the actual use of devices.The performance of schottky contact directly affects the performance of devices.In this paper,the W/C laminated structure is used as the contact between the contact metal and the 4H-SiC to form rectifier characteristics,and the high temperature characteristics of the experimental samples are analyzed and studied.1.In this paper,the Schottky properties of W/C laminated/4H-SiC and W/4H-SiC samples were analyzed by rapid thermal annealing at different temperatures.Experiments have found that W/C laminates/4H-SiC:The barrier height of the unannealed samples was0.91eV and the ideal factor was 1.13.After annealing,the barrier increased,the ideal factor decreased,and the reverse leakage current showed a slight decrease,indicating that the contact characteristics were improved.When the annealing temperature up to 1000?,the barrier shows decline trend.When the annealing temperature rose to 1200?,rectifier features of the sample disappear.Annealing temperature up to 600?,the barrier is 1.17eV,and ideal factor achieve the optimal value of 1.03.When annealing temperature continues to rise,barrier height is 1.23 eV,ideal factor up to 1.15,the sample reach maximum potential barrier.W/4H-SiC:When the annealing temperature is 600?,the barrier of the sample is not obvious changes,barrier height at around 1.12 eV.With the Annealing temperature continue rise,the barrier become larger.And the sample lost the rectifier features when the annealing temperature up to 1200?.SEM and AFM tests were carried out on the samples,and the results showed that rapid thermal annealing improved the roughness of the contact surface,the electrode became smooth,and nanometer particles appeared on the surface with the deterioration of the rectifier characteristics.Through the analysis of XRD energy spectrum,it is judged that it is related to the new phase W₂C generated at the contact surface.2.In order to explore the rectification characteristics of experimental samples with the change of test temperature,the ambient temperature from normal temperature gradually increased to 150?,the test process observed that with the increase of the test temperature of each sample barrier increased,the ideal factor approaching 1,which shows that the carrier transport is mainly determined by the thermal electron emission model at high temperature.With the increase of the test temperature,the reverse leakage flow increases gradually,in which the reverse leakage current of the annealed sample changes the most,which is related to the low barrier height ideal factor of the non-annealed sample.The sample of 600?annealing changed little with the increase of the test temperature,but the reverse leakage current increased greatly,and it can be judged that the potential stability of the sample is better,and the reverse leakage current of the sample with 750?annealing is the smallest,which is related to the increase of the potential barrier with the increase of the test temperature.3.Using the Werner's model and the Tung's model to analyze the homogeneity of the sample's Schottky contact barrier,and it is found that the sample which is the W/C laminated structure has the best homogeneity when the annealing temperature between600?-800?,and the surface roughness form the AFM test is reduced to about 4nm.The inhomogeneity of the W/4H-SiC experimental samples did not appear evenly at 1000?.Comparing the inhomogeneity of the sample with the reverse leakage current,it can be found that under the condition that the average barrier is similar,the better the distribution uniformity of the barrier,the greater the reverse leakage current with the temperature,in which the higher the potential of the sample reverse leakage current with the temperature changes.Ultraviolet illumination is applied to the sample,the light and dark current generated by the sample is analyzed,and the detection rate and response degree are calculated,in which 750?temperature annealing sample in the W/C laminated/4H-sample changes from 3.3mA/W to 3.8mA/W with the increase of temperature,and the detection rate is at room temperature 6.63x10¹¹cmHz^1/2W drops to 3.33x10¹¹cmHz^1/2W.In this paper,W/C laminated structure is proposed as contact between metal and N-type4H-SiC to form rectifier contact,after 750?rapid thermal annealing,the sample presented good Schottky rectifier contact and maintain the stability of high temperature,and pure tungsten as an outstanding metal compared to the barrier has a small decline.The power consumption of the contact application in the power device is reduced,and the response and detection rate of the sample are lower with the test temperature after ultraviolet light irradiation,which has guiding significance and value for the application of SiC devices at high temperature.