Thermal stability study of n-type and p-type ohmic contacts simultaneously formed on 4H-SiC.

In this paper, Pt/TaSi 2 /Ni/Ti/Ni/SiC and Pt/Ti/SiC simultaneous ohmic contacts to n-type and p-type 4H-SiC are studied. The thermal stability and electrical characteristics of the ohmic contacts are investigated and compared after being aged at 500 °C for 300 h in air. The n- and p-type Pt/Ti/SiC ohmic contact failed after 100 h and after 200 h, respectively. While the Pt/TaSi 2 /Ni/Ti/Ni/SiC samples exhibits a good thermal stability and high temperature electrical characteristics, with a relatively small increase of the specific contact resistance (SCR) in the initial 50 h and then remains stable in the rest of the thermal aging duration. SEM analysis reveals that the surface morphologies of Pt/TaSi 2 /Ni/Ti/Ni/SiC samples keep smooth and stable during the aging process. According to AES analysis, the main reason of electrical characteristics degradation is the oxidation on the metal/4H-SiC interface during the aging process. Also, at the expense of the TaSi 2 layer oxidization, the diffusion rate of oxygen atoms towards the SiC are slowed down, and therefore, the metal/4H-SiC interface quality was not affected by oxidation problems and extending the life of ohmic contact in air at 500 °C. Experimental results indicate that the Pt/TaSi 2 /Ni/Ti/Ni/SiC simultaneous ohmic contacts to both n- and p-type SiC are promising to be used for high temperature and harsh environment SiC-based devices. [ABSTRACT FROM AUTHOR]