Abstract. In this paper, the transport properties of alloyed Ti/Al Ohmic contacts formed on p-type Al-implanted silicon carbide (4H-SiC) were studied. The morphology of p-type implanted 4H-SiC was controlled by using a capping layer during post-implantation activation annealing at 1700°C. The different morphological conditions does not affect the macroscopic electrical properties of the implanted SiC (like the sheet resistance or the mobility). On the other hand, the improved morphology of implanted SiC allows to achieve a flatter Ti/Al surface and a lower specific contact resistance. The temperature dependence of the specific resistance of the contacts was studied to get physical insights into the carrier transport mechanism at the metal/SiC interface. The fit comparing several models shows that thermionic field emission is the dominant transport mechanism through the metal/SiC interface, and that a reduction of the barrier height from 0.51eV to 0.46 eV is associated to the improvement of the Ohmic properties. Transmission Electron Microscopy analysis showed the presence of a laterally inhomogeneous microstructure of the metal/SiC interface. The reduction of the barrier height could be correlated with the different microstructure of the interfacial region.

The mechanism limiting the channel mobility in metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated in Al-implanted 4H-SiC is discussed comparing different post-implantation annealings. In spite of the improved interfacial morphology in carbon capped samples during annealing, the observed reduction of the mobility (from 40 to 24 cm2 V−1 s−1) suggests that interfacial roughness does not significantly impact the transport in the channel. Furthermore, the temperature dependence of the mobility demonstrates that Coulomb scattering is the main degradation mechanism due to the presence of trapped charges at the SiO2/SiC interface.

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