High temperature and high power stability investigation of Al-based ohmic contacts to p-type 4H-SiC

Three types of low resistivity Al-based ohmic contacts to p-type 4H-SiC, Au/Al/Si, Au/AlSiTi and Au/Ti/Al have been studied. Reproducible contact resistivity of 8.30×10^-5 Ωcm², 6.42×10^-5 Ωcm² and 1.42×10^-5 Ωcm² has been obtained for Al/Si, AlSiTi and Al/Ti contacts, respectively. The investigation of the thermal properties of Al-based contacts shows that addition of Ti to the contact composition improves its stability at ageing temperatures as high as 700°C, at operating temperatures up to 450°C and current densities of 10³ A/cm². XPS analysis of as-deposited and annealed contacts has been performed to explain the observed thermal properties.