High-purity semi-insulating 8° off-axis 4H-SiC was implanted with Al+ at different doses and energies to obtain a dopant concentration in the range of 5 × 1019–5 × 1020 cm−3. A custom-made microwave heating system was employed for post-implantation annealing at 2,000 °C for 30 s. Sheet resistance and Hall-effect measurements were performed in the temperature range of 150–700 K. At room temperature, for the highest Al concentration, a minimum resistivity of 3 × 10−2 Ω cm was obtained, whereas for the lowest Al concentration, the measured resistivity value was 4 × 10−1 Ω cm. The onset of impurity band conduction was observed at around room temperature for the samples implanted with Al concentrations ≥3 × 1020 cm−3. Vertical p +-i-n diodes whose anodes were made by 1.5 × 1020 cm−3 Al+ implantation and 2,000 °C/30 s microwave annealing showed exponential forward …