Single crystalline 3C-SiC layers were grown on a porous Si seed using a single gas source, trimethylsilane. The method is environmentally friendly, utilizes a non-toxic gas, and is economical. The porous Si layers were made by anodizing p-type Si(100) wafers in a mixture of hydrofluoric acid and ethanol. The SiC was grown in a high vacuum system that was converted into a low-pressure CVD reactor and was fitted with a resistive heating stage capable of heating the samples up to 1250 degreesC. The formation of stoichiometric SiC was confirmed by secondary ion mass-spectrometry (SIMS) while the crystal structure was examined by transmission electron microscopy (TEM) and X-ray diffraction. Fourier transform infrared spectroscopy (FTIR) showed a strong peak at 800 cm(-1) which corresponds to the Si-C vibrational mode. Atomic force microscopy (AFM) showed the formation of rough surfaces for thin SiC layers and large flat terraces for thick SiC layers. TEM selected area diffraction indicates the formation of fully relaxed single crystalline 3C-SiC(100) on Si(100) wafers. However, large area X-ray diffraction suggests the presence of other crystal orientations within the dominating SiC(100) layer. Heterojunction Si/SiC diodes were fabricated, which displayed a soft breakdown voltage as high as 375V. Growth of single crystalline AlN on Si and SiC was also demonstrated.