An inductively heated furnace and an ultra-fast microwave heating system have been used for performing post implantation annealing processes of P+ implanted semi-insulating <0001> 4H SiC at 1800-1950°C for 5 min and 2000-2050°C for 30 s, respectively. Very high P+ implantation fluences in the range 71019 81020 cm-3 have been studied. The annealing processes in the inductive furnace and the one at the lower temperature in the microwave furnace show a saturation in the efficiency of the electrical activation of the implanted P+ that is bypassed by the microwave annealing process at the higher temperature. The measured electron mobility values versus electron density are elevated in all the studied samples and for every post implantation annealing process. This has been ascribed to an elevated implanted crystal recovery due to the very high annealing temperatures > 1800°C.