Low resistance p-layers are achieved in this paper using a graphite cap to protect SiC surface from out-diffusion of Si during high temperature post-implantation annealing, which is carried out to maximize the activation of Al dopant in 4H-SiC. With a graphite layer converted from photoresist, as high as 1700 and 1800oC post-implantation annealing is able to be used. Low RMS roughness of surface after high temperature annealing shows the effectiveness of the graphite cap. Small sheet resistance and resistivity are also achieved from the high temperature annealing. At room temperature, sheet resistances of 9.8 and 1.3 k/□, and the corresponding resistivities of 235 and 31 m-cm are obtained from 1700 and 1800oC annealed samples, respectively. The Al ionization energy extracted from Arrhenius plot is also close to the typical reported values. Therefore, it can be concluded that, using graphite cap could help to activate the Al dopant effectively during high temperature annealing.