The growth of cubic aluminum nitride (AlN) and cubic gallium nitride (GaN) is studied. The effects of ambient pressure and substrate temperature on the structure of the AlN and GaN films are systematically investigated. It is shown that the films are amorphous when the temperature and the pressure are too low. Cubic AlN is obtained at a temperature of 800°C and a pressure of 0.2 Torr. Cubic GaN can be obtained at 600°C with a cubic AlN buffer layer.