Sulfur Passivation Research Effect On 6H-SiC Surface

The existence of the surface states seriously affected the contact characteristics for SiC devices.The existence of the surface states is inevitable in the SiC semiconductor device,because breaking chemical bonds is exist or surface dangling bonds does not match with internal,these surface dangling bonds will introduce a lot of extrinsic energy states in the bandgap,which is often said interface states and surface states,they are lead to surface and interface with chemistry,electrical and optical properties of atoms different from body.The surface state or the interface state density is large,it can cause the surface Fermi level pinning and band bending deformation,saturated dangling bonds can effectively reduce the interface state or surface states to improve devices nature has very important significance.This paper focuses on the study of S passivation process for SiC surface and analyzes the passivation effect.Experiment with different concentrations of NH3·H2O and(NH4)2S mixed solution passivated SiC surface.Optimum passivation process parameters by I-V test,extract barrier height and XPS characterization tests to show passivation effect,improve the passivation mechanism of using I-V.The main contents and results are as follows:1?Process research and characterization of sulfur passivation on Si surface of SiC.Using different concentrations of the mixed solution passivated Si surface,research can get the best parameters:passivation temperature is 60? passivation time is 30min,NH3 H2O concentration is 2.4mo1/L,NH4)2S concentration is 0.22mol/L,compare the passivation effect through I-V test compare reverse saturation current,and the use of XPS test parameters under optimal passivation,the sample by optimum parameters passivation analysis the surface shows the presence of S-Si bonds,further proof S passivated SiC surface is effective.2?A preliminary study for C surface passivation of SiC,compared to Si surface passivation of SiC,results show that Si surface of SiC passivation effect is better than C surface.3?Passivation Mechanism about S passivated SiC surface.Production of Al/SiC Schottky contact,analysis before and after S passivation Al/SiC Schottky barrier height of the contact,the barrier height extracted results showed the barrier height increases.In order to study the mechanism,analysis surface Fermi level and the surface density changes using XPS.The results show that the sample after passivation of the Fermi level moved 0.28eV to the conduction band bottom,illustrating the surface state density is reduce.And to further discuss the relationship between Al/SiC barrier height and surface density of states,and found the experimental results is consistent with Cowley and Sze theoretical barrier.