A microwave heating technique has been used for the electrical activation of Al+ ions implanted in semi-insulating 4H-SiC. Annealing temperatures in the range of 2000–2100 C and annealing time of 30 s have been used. The implanted Al concentration has been varied from 5× 10 19 to 8× 10 20 cm-3. A minimum resistivity of 2× 10-2 Ω centerdot cm and about 70% electrical activation of the implanted Al have been measured at room temperature for an implanted Al concentration of 8× 10 20 cm-3 and microwave annealing at 2100 C for 30 s.