The ability to control the electrical resistivity of semiconducting tetrahedral amorphous carbon (ta-C) films is reported. Phosphorus is incorporated during film growth from a plasma formed with a cathodic vacuum arc by using a phosphorus-containing carbon cathode. By changing the P content in the cathode from 0-1% mass the room temperature resistivity of the films can be changed from 10⁷ Omega cm to 5 Omega cm. Electron energy-loss spectroscopy shows that incorporation of P does not change the amorphous tetrahedral nature of the carbon films deposited by the vacuum arc method.