Free standing wafers of the cubic polytype of silicon carbide (3C-SiC) grown on micromachined silicon substrates can be a platform for new power electronic devices, provided that suitable device fabrication processes are understood and optimized. In this frame, p-type doping is still an open issue, as results on the electrical activation of ion implanted Al in 3C-SiC are limited. This work analyses high level p-type doping with post-implantation annealing carried out at temperatures in the range 1650-1850 °C with different durations. A coherent picture emerges, showing that the resulting resistivity in 3C-SiC Al-implanted layers is higher than the one obtained in 4H-SiC implanted layers, the result being ascribed to low carrier mobility and possibly presence of compensation centers, rather than to poor Al electrical activation. The reported results highlight the importance of working on material and processing optimization.