Mass transport in the epitaxial lateral overgrowth of gallium nitride

We have investigated lateral transport mechanisms in epitaxial lateral over growth (ELO) of GaN grown by Metal organic chemical vapor deposition (MOCVD ). Portions of a pre-grown GaN buffer layer are patterned with a dielectric mask material, silicon nitride. Further growth of GaN occurs selectively o n exposed areas of the underlying buffer layer, and not on the dielectric m aterial. Growth-rate enhancement on the exposed GaN is observed due to late ral transport of material from the masked regions. We describe experiments to distinguish whether the lateral transport of material occurs via gas-pha se diffusion or surface diffusion, either on the mask itself or on the epit axial material. Deep trenches were etched into the wafer prior to the ELO g rowth, designed to interrupt lateral transport if it were occurring by diff usion along the surface. ELO growth rate profiles on exposed line patterns and on larger area blanket growth zones were examined with and without the trenches. Growth profiles were virtually identical independent of the prese nce of the trench features. These results indicate that gas-phase diffusion dominates the transport of material during GaN ELO. (C) 2001 Elsevier Scie nce B.V. All rights reserved.