Improvements on the electrical and luminescent properties of reactive molecular beam epitaxially grown GaN films by using AlN-coated sapphire substrates

The electrical and luminescent properties of the GaN epitaxial films grown on AlN-coated sapphire by reactive molecular beam epitaxy have been studied. The GaN films on AlN epitaxial films have larger Hall mobilities and show more intense cathodoluminescence peaks at a wavelength of 360 nm than those of the GaN films grown directly on sapphire, which suggests that the crystal qualities of GaN films are improved by use of AlN-coated sapphire as substrates. The lattice matching and small difference of the thermal expansion coefficients between GaN and AlN are considered to result in the improvements.