Laser alloying nickel on 4H-silicon carbide substrate to generate ohmic contacts

To obtain ohmic contacts on silicon carbide semicondanneuctors commonly a thin metal layer is deposited onto the semiconductor wafer, followed by a rapid thermal process to transform the resulting Schottky diode into an ohmic contact. Here, we report on an alternative laser based process replacing the conventional rapid thermal treatment. A continuous wave infrared fiber laser is employed to locally alloy nickel coated silicon carbide to an ohmic contact. Our results show that ohmic contacts are achieved with laser powers between 100 W and 300 W over an irradiated area on the order of 7 mm diameter. Electrical resistances of the generated ohmic contacts are measured down to 6.5 ohm, depending on laser power. Temperature dependent measurements of the resistance reveal a negative temperature coefficient of 11 ohm m/K.