Gallium nitride devices are formed on a diamond substrate, such as for light emitting diodes as a replacement for incandescent light bulbs and fluorescent light bulbs. In one embodiment, gallium nitride diodes (or other devices) are formed on diamond in at least two methods. A first method comprises growing gallium nitride on diamond and building devices on that gallium nitride layer. The second method involves bonding gallium nitride (device or film) onto diamond and building the device onto the bonded gallium nitride. These devices may provide significantly higher efficiency than incandescent or fluorescent lights, and provide significantly higher light or energy density than other technologies. Similar methods and structures result in other gallium nitride semiconductor devices.