Zinc-blende and wurtzite AlxGa1−xN bulk crystals grown by molecular beam epitaxy

There is a significant difference in the lattice parameters of GaN and AlN and for many device applications AlxGa1−xN substrates would be preferable to either GaN or AlN. We have studied the growth of free-standing zinc-blende and wurtzite AlxGa1−xN bulk crystals by plasma-assisted molecular beam epitaxy (PA-MBE). Thick (∼10 μm) zinc-blende and wurtzite AlxGa1−xN films were grown by PA-MBE on 2-in. GaAs (0 0 1) and GaAs (1 1 1)B substrates respectively and were removed from the GaAs substrate after the growth. We demonstrate that free-standing zinc-blende and wurtzite AlxGa1−xN wafers can be achieved by PA-MBE for a wide range of Al compositions.