Highly conducting boron-doped microcrystalline silicon carbide (mu c-SiC:H) thin films have been prepared by mercury sensitised photochemical vapor deposition. The chamber pressure was identified as one of the most crucial parameters governing the microcrystalline growth as well as the dopant incorporation in the microcrystalline thin films. Raman studies show the crystalline size and volume fraction decreases with increasing pressure. Transmission electron microscopy of such films reveal that the crystalline phase contains silicon only, so that carbon is incorporated only in the amorphous phase. The presence of carbon in these films was confirmed by secondary ion mass spectroscopy. There is an optimum pressure (0.5 Torr), depending upon the other deposition parameters, for which the conductivity of p-type mu c-SiC:H film is highest (1.2 x 10(-4) S cm(-1)).