Demonstration of crystal-vapor equilibrium leading to growth blockade of GaN during selective area growth

The synthesis of GaN by selective area growth using Hydride Vapor Phase Epitaxy (SAG-HVPE) is reported for stripes patterned along < 1 (1) over bar 00 > and < 11 (2) over bar0 > GaN on c-plane sapphire substrates. A systematic control of the GaN morphologies was carried out by both cross-sectional and surface Scanning Electron Microscopy (SEM). A complete HVPE cartography of GaN-SAG revealed domains of zero growth rates at high concentration of hydrogen in the carrier gas. The determination of the mechanisms that govern the growth of GaN morphologies was particularly emphasized. A theoretical model based on thermodynamic and kinetic analyses of the grown (0001) GaN layers was discussed, in combination with experiments on unmasked (0001) GaN and patterned GaN/c-plane sapphire substrates. Long HVPE runs were performed to demonstrate that the prevailing growth mechanism, for high hydrogen concentration in the carrier gas, is a mechanism based on a dechlorination by GaCl2 gas species. This mechanism leads to growth blockade of GaN growth and constitutes a very interesting issue for shaping GaN material as an alternative to top-down micro- and nano-technologies. (C) 2012 Elsevier B.V. All rights reserved.