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AlGaN/4H–SiC heterojunction diodes with varying composition of Al have been fabricated. Five different compositions were investigated, GaN, Al0.1Ga0.9N, Al0.15Ga0.85N, Al0.3Ga0.7N, and Al0.5Ga0.5N, along with a 4H–SiC homojunction diode for comparison. The turn on voltage was around 1 V, and the ideality factor between 1 and 2 for all heterojunction diodes except for the Al0.3Ga0.7N diode. This diode had an ideality factor between 2 and 3, and also showed a much lower series resistance, indicating a change in transport mechanism across the junction. A tunnel assisted recombination model was analyzed and compared to the extracted values of the GaN diode. The model agreed well with both current–voltage and capacitance–voltage measurements for this diode. This model was not applied to the other samples, since their characteristics could not be explained by a simple mechanism.

We report on the investigation of epitaxial TiC ohmic contacts to Al ion implanted 4H–SiC. TiC ohmic contacts were formed by coevaporation of Ti and C60 at low temperature (<500 °C). A sacrificial silicon nitride (Si3N4) layer was deposited on the silicon carbide substrate prior to Al implantation in order to reach a high Al dopant concentration at the surface while maintaining a low dose. The combination of epitaxially grown TiC and the silicon nitride layer resulted in a promising scheme to make low resistivity ohmic contacts. The lowest contact resistivity (ρC) and sheet resistance (Rs) of the implanted layer at 25 °C were as low as 2×10−5 Ω cm2 and 0.6 kΩ/□, respectively.