Molecular beam epitaxy of free‐standing bulk wurtzite Al_xGa_1‐xN layers using a highly efficient RF plasma source

Abstract

Recent developments with group III nitrides suggest AlxGa1‐xN based LEDs can be new alternative commercially viable deep ultra‐violet light sources. Due to a significant difference in the lattice parameters of GaN and AlN, AlxGa1‐xN substrates would be preferable to either GaN or AlN for ultraviolet device applications. We have studied the growth of free‐standing wurtzite AlxGa1‐xN bulk crystals by plasma‐assisted molecular beam epitaxy (PA‐MBE) using a novel RF plasma source. Thick wurtzite AlxGa1‐xN films were grown by PA‐MBE on 2‐inch GaAs (111)B substrates and were removed from the GaAs substrate after growth to provide free standing AlxGa1‐xN samples. Growth rates of AlxGa1‐xN up to 3 µm/h have been demonstrated. Our novel high efficiency RF plasma source allowed us to achieve free‐standing bulk AlxGa1‐xN layers in a single day's growth, which makes our MBE bulk growth technique commercially viable.