In-situ optical monitoring of surface morphology and stoichiometry during GaN metal organic vapor phase epitaxy

The surfaces during GaN metalorganic vapor phase epitaxy MOVPE.were in-situ monitored by shallow-angle reflectance using ultraviolet uv. light and were compared between the growths on sapphire and on 6H–SiC substrates. By this method, stable monitoring is possible without an influence of strong and visible black-body radiation from the substrate heated to high temperatures. The growth-rate was successfully monitored by optical interference, and the morphological change was detected by the reflectivity change due to Rayleigh scattering. The surface of AlN buffer layer deposited on the 0001.sapphire substrate roughens at the thickness thinner than 30 nm, when the temperature is raised to the growth temperature of GaN. From the period of interference oscillation observed, the growth-rate on the 0001.SiC substrate is almost constant but, on the sapphire substrate, the growth-rate is about 14% decelerated in the thickness range approximately from 70 to 140 nm due to the coalescence of islands by lateral growth. Surface photoabsorption SPA.was applied to monitor the chemical stoichiometry of GaN surface during growth. It is found that the uniform growth dominated by step-flow mode is achieved by Ga-rich stoichiometry in H2 carrier gas. The surface process during uniform growth of GaN is also proposed. q2000 Elsevier Science B.V. All rights reserved