Zinc‐blende (cubic) GaN bulk crystals grown by molecular beam epitaxy

We have studied the growth of zinc-blende (cubic) GaN and AlxGa1-xN layers and bulk crystals by molecular beam epitaxy (MBE). MBE is normally regarded as an epitaxial technique for the growth of very thin layers with monolayer control of their thickness. However, we have used the MBE technique for bulk crystal growth and have produced GaN layers up to 100 μm in thickness. Thick, cubic GaN films were grown on semi-insulating GaAs (001) substrates by a modified plasma-assisted molecular beam epitaxy (PA-MBE) and were removed from the substrate after the growth. The resulting free-standing GaN wafers with thicknesses in the 30–100 μm range may be used as substrates for further epitaxy of cubic GaN-based structures and devices. We have demonstrated the scalability of the process by growing GaN layers up to 3” in diameter. We have developed procedures to cleave the wafers and to polish them to produce epi-ready surfaces. We have demonstrated that the PA-MBE process we have developed also allows us to achieve free-standing zinc-blende AlxGa1-xN wafers over the entire composition range from GaN to nearly pure AlN. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)