Properties of AlxGa1−xN films prepared by reactive molecular beam epitaxy

Single-crystal films of the solid solution AlxGa1−xN of the entire composition range have been fabricated on sapphire and silicon substrates by reactive molecular beam epitaxy (MBE) at 700 °C. The properties of the films have been studied by the reflection high energy electron diffraction technique, x-ray diffraction, and electrical and optical measurements. The lattice constant of the film is not a linear function of the composition, and the fundamental absorption edge also shows nonlinear dependence on the composition. The narrow intense peak of the cathodoluminescence concerned with the band to band or shallow impurity band transition, varies from 3.4 to 6 eV with the composition, which suggests the feasibility of AlxGa1−xN films grown by reactive MBE for optical devices in the ultraviolet spectral region.