In situ XPS spectroscopic study of thermal stability of W/Ni bilayer Ohmic contact to n-type 4H-SiC

摘要

The thermal stability of Ohmic contacts to η-type 4H-SiC using Au/Pt/Ni and Au/Pt/W/Ni layers has been systematically investigated after long-time aging in air at 300 °C and 400 °C. The specific contact resistance (ρ_c) is calculated from current-voltage (I-V) curves. The content of carbon in the contact layer is measured by Raman spectroscopy. A transmission electron microscope and a energy dispersive spectrometer are used to characterize the interface morphology and component distribution. The phase composition of the contact layer at different depths is analyzed in situ by x-ray photoelectron spectroscopy. It is found that Ni_(2-x)W_xSi decomposition plays an important role in improving the thermal stability of the Ohmic contact. The decomposition products (Ni, W, and Si atoms) react with oxygen, and the diffusion of oxygen to the Ni_2Si/SiC interface can be reduced to some extent. Compared to Au/Pt/Si/SiC, the Au/Pt/W/Ni/SiC Ohmic contact exhibits better thermal stability. It is expected that the W/Ni/SiC Ohmic contact will be very suitable for high temperature applications.