Free-standing zinc-blende (cubic) GaN layers and substrates

It has been demonstrated that it is possible to grow by molecular beam epitaxy bulk free-standing zinc-blende (cubic) GaN layers. Such layers have potential applications as lattice matched substrates for growth of non-polar cubic GaN device structures of improved performance. We present the data from characterisation measurements that confirm the cubic nature of the GaN crystals and show that the fraction of the hexagonal material is not more than about 10% in the best 50 μm thick free-standing GaN samples. Our research is aimed at increasing the size of the free-standing cubic GaN layers in order to make this technology suitable for the commercial production of substrates and we have now demonstrated the growth of 100 μm thick, 2-in diameter GaN substrates.