Aluminum and boron doping by co-diffusion into n-type 4H-SiC (0001), (000 (1) over bar) and (1 (1) over bar 00) face (p-face) substrates was carried out at the temperatures of 1900-2000degreesC. Secondary ion mass spectroscopy (SIMS) was employed to obtain the impurity profiles, which showed that there was no significant difference between concentration depth profiles of the dopants in Si- and C-face samples. However, significantly enhanced diffusion of these impurities into (1 (1) over bar 00) face sample was observed. Based on the SIMS data, diffusion coefficients of boron and aluminum in the (1 (1) over bar 00) face SiC was calculated and reported for the first time.