**2. Materials and Methods**

Transfer length method (TLM) structures with increasing pad distances (30 µm to 480 µm) were fabricated on n− doped 4H-SiC epitaxial layers in order to investigate the contact formation mechanism of Ti/Al based ohmic contact. Al implantation and subsequent high temperature annealing was used to create samples with p<sup>+</sup> doped regions and Al surface concentrations between 3.3 <sup>×</sup> <sup>10</sup><sup>18</sup> cm−<sup>3</sup> and 5.0 <sup>×</sup> <sup>10</sup><sup>19</sup> cm−<sup>3</sup> . After depositing and structuring a SiO<sup>2</sup> passivation layer, a metal stack consisting of 80 nm Ti and 300 nm Al was deposited and patterned using a lift-off process. Subsequently ohmic contact formation was done by rapid thermal annealing (RTA) at 980 ◦C in Ar atmosphere. Finally, metal pads for electrical measurements were deposited and structured. A more detailed description of the fabrication process of sample C can be seen elsewhere [18]. Table 1 gives an overview of the fabricated sets of samples and their fabrication parameters.

**Table 1.** Parameters of the fabricated sets of samples.


By using 4-point I-V-measurements (Keithley 4200 Parameter Analyzer, Keithley Instruments, USA) at different temperatures (300 K to 450 K), the fabricated TLM structures were electrically characterized and the sheet resistance *Rsh*, the contact resistance *R<sup>C</sup>* as well as the specific contact resistance *ρ<sup>C</sup>* were determined in the given temperature range.

Focused ion beam (FIB) (Helios Nanolab 600, FEI, USA) as well as transmission electron microscopy (TEM) analysis were done to determine the thickness of the Ti3SiC<sup>2</sup> layer (approx. 100 nm) as well as its stoichiometry.
