Properties of carbon-doped GaN

The properties of carbon-doped GaN epilayers grown by molecular-beam epitax y have been studied by temperature-dependent resistivity, Hall-effect measu rements, x-ray diffraction, and by photoluminescence spectroscopy. Carbon d oping was found to render the GaN layers highly resistive (> 10(8) Omega cm ) and quench the band edge excitonic emissions. Yellow luminescence is stil l present in carbon-doped GaN layers. The highly resistive state is interpr eted as being caused by direct compensation by the carbon acceptors and by the consequently enhanced potential barrier at the subgrain boundaries. Evi dence of dislocations joining to form potential barriers along the subgrain boundaries was observed in photoassisted wet etching experiments on electr ically conducting GaN layers. GaN films grown on insulating carbon-doped ba se layers are of excellent transport and optical properties. (C) 2001 Ameri can Institute of Physics.