Activation of aluminum implanted at high doses in 4H–SiC

We report an investigation of the electrical activation of aluminum implanted at high dose in 4H–SiC. We show that at reasonably high temperature implantation and annealing conditions, one activates about 37.5% of the implanted species. Of course, the final (concentration-dependent) activation ratio differs slightly from this average value but varies only between 0.5 and 0.25 when the targeted concentration increases from 3.33×1018 to 1021 cm−3. Provided a standard mobility can be maintained, this results in fairly low sheet resistance. The best (lowest) value obtained in this work is 15 mΩ cm at 700 K (95 mΩ cm at room temperature) for a 190-nm-thick layer implanted with 1021 atoms cm−3. In MESA-etched p–n junctions with a 100 μm diameter, this resulted in a typical on-resistance of 1.5 mΩ cm2, mainly limited by the substrate and n− epitaxial layer.