High-quality GaN films grown on Si(111) by a reversed Stranski-Krastanov growth mode

High-quality GaN film has been successfully grown on Si(111) substrates by metal-organic vapor phase epitaxy (MOVPE). Low-temperature GaN layers were inserted into high-temperature grown GaN as the intermediate layers. High-resolution transmission electron microscope (HRTEM) images revealed that the GaN tends to form large islands (∼25-50 nm) during temperature cycles. The formation of islands plays an important role in improving the crystal quality. Then, layer-by-layer growth was enhanced by ramping temperature to 1050 °C and increasing the growth rate. Finally, a mirror-like smooth surface was obtained. We describe the observed change in growth mode from three-dimensional (3D) to two-dimensional (2D) as a reversed Stranski-Krastanov growth mode. The ω-rocking curve measurement gave a full width at half-maximum of 500 arcsec for GaN grown on Si. This is comparable to GaN grown on sapphire and is among the best results reported. The detailed epitaxial growth mechanism of GaN on Si (111) is also discussed.