Aluminum doped (Al-doped) p-type nc-3C-SiC:H films were successfully depsoited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) at a low substrate temperature of about 360°C using dimethylaluminum hydride (DMAH) as an Al dopant. Dark conductivity and activation energy of the films were strongly influenced by H2/MMS gas flow ratio. A dark conductivity of a 27-nm-thick film was improved from 1.5×10-5 to 6.9×10-4 S/cm by changing H2/MMS gas flow ratio from 6.4×103 to 8.5×103. Activation energy was found to be 265 meV for the optimized Al-doped nc-3C-SiC:H. Clear rectifying characteristics of J-V characteristics of Al-doped nc-3C-SiC:H / n-type c-Si heterojunction diodes confirmed the p-type nature of Al-doped nc-3C-SiC:H. These result indicates that Al-doped nc-3C-SiC:H is promising for p-type window layer of a top cell of multi-junction silicon-based thin-film solar cells.