The Hall scattering factor of holes rH,h(T) in 4H- and 6H-SiC is determined by comparing the temperature-dependent free hole concentration p(1/T) obtained from Hall effect and from the neutrality equation with defect parameters, which are independently determined by SIMS and C-V measurements. rH,h(T) strongly deviates from 1 and assumes values between 1.4 and 0.5 at temperatures ranging from 100K to 800K. rH,h(T) is identical for 4H-and 6H-SiC within the measurement uncertainty. Al-doped SiC epilayers of the 3C-, 4H- and 6H-polytype were investigated with admittance spectroscopy and DLTS prior to and subsequent to processing steps. Depending on the SiC polytype, a different number of shallow acceptors is observed, which are thermally stable up to high temperatures (1700°C).