Thin Solid Films, Vol.515, No.2, 603-606, 2006
Substrate pre-treatment and initial growth: Strategies III-nitride growth on sapphire by molecular towards high-quality beam epitaxy
Sapphire substrates annealed at 1200 degrees C in N-2:O-2 (3 : 1) developed terrace-and-step morphology, ideal for III-nitride growth by molecular beam epitaxy. In situ treatment of sapphire substrates, using Ga deposition and desorption prior to growth, is shown to be negative for GaN growth. Nitridation transforms the sapphire substrate surface to a lateral structure similar to AlN (mismatch < 2.5%). The surface lattice parameters after nitridation did not depend on the substrate temperature. AlN nucleation layer growth conditions have been optimized for growth of GaN. Ideal Al/N flux ratio was found to be 0.6 for a 9 nm thick nucleation layer. (c) 2006 Elsevier B.V. All rights reserved.
Keywords:crystal morphology;crystal structure;molecular beam epitaxy;semiconducting gallium compounds;semiconducting III-V materials