Results and discussion
At the first stage we carried out PA-MBE growth of thin (~1 μm) wurtzite AlxGa1−xN layers on two-in. diameter (111)B GaAs substrates for AlN fractions ranging from 0 up to 0.5. This substrate orientation was chosen in order to initiate the growth of the hexagonal phase of material. Wurtzite GaN buffers, of thickness ~50 nm, were deposited before the growth of all the AlxGa1−xN layers.