Influence of Ni and Nb thickness on low specific contact resistance and high-temperature reliability of ohmic contacts to 4H-SiC

Abstract

The influence of Ni and Nb thickness on the electrical properties and high-temperature reliability of Ni(x)/Nb(100 – x)/n-type 4H-SiC ohmic contacts, where x = 25, 50 or 75 nm, was investigated. Two-dimensional X-ray diffraction, hard X-ray photoelectron spectroscopy and transmission electron microscopy analyses indicated that a relatively high Ni concentration had a strong influence on low specific contact resistance due to the greater formation of Ni2Si at the contact interface, whereas a higher density of Nb improved the ability to collect excess carbon atoms by the formation of Nb6C5 at the interface, ensuring high-temperature reliability of the contacts. The experimental results showed that the Ni(50)/Nb(50)/4H-SiC ohmic contact is a potential candidate for high-temperature and harsh environment applications.