Growth mechanisms of (00.1)GaN substrates in the hydride vapour-phase method:: surface diffusion, spiral growth, H2 and GaCl3 mechanisms

The theoretical model developed to account for the {0 0 1}GaAs growth in the AsCl3/H-2 and AsCl3/He systems is applied to the (0 0.1)GaN growth by hydride vapour-phase epitaxy in H-2 or neutral carrier gases. The two growth mechanisms of chlorine desorption in HCl and in GaCl3, and the step flow and spiral growth processes are investigated. The model was improved by adding a step of hydrogen adsorption on adsorbed chlorine atoms, and by deducing all pre-exponential kinetic factors from the partition functions. The mass transfer effect is approached by using the same boundary layer model as in GaAs. The drastic effect of extraneous depositions on the growth rate is estimated by introducing the fraction of source HCl flow consumed as GaCl3 and by applying the species balance equations. (C) 1999 Elsevier Science B.V. All rights reserved.