Low temperature Ni/Si/Al ohmic contacts to p-type 4H-SiC

Abstract

In this paper, we studied the electrical and structural properties of Ni/Si/Al Ohmic contacts to p-type 4H-SiC. The p-type epilayer (NA = 1 × 1019 cm−3) was grown on the N-type epilayer with Al dopants. The properties of Ni/Si/Al contacts were analyzed by changing the thickness of Si film and the annealing temperature. After annealing at 700 °C, the Ni/Si/Al contact forms ohmic contact. Compared to Ni/Al contacts, Ni/Si/Al ohmic contacts are formed at lower annealing temperature. The contact resistivity of Ni/Si/Al (80/20/100 nm) contact is 1.3 × 10−4 Ω·cm2 after annealing at 800 °C. X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) are used to analyze the microstructure and observe the surface topography. The results show that Ni and Si react at low temperature to form Ni2Si, which is the reason for the formation of Ni-based ohmic contacts. At the same time, the addition of the Si layer weakens the reaction between Ni and SiC, which reduces the generation of free C elements. The Ni/Si/Al contact shows better ohmic contact characteristics.