AVS 47th International Symposium
    Semiconductors Thursday Sessions
       Session SC+SS+EL-ThA

Invited Paper SC+SS+EL-ThA5
Crystal Growth Kinetics and Transport in GaN Epitaxial Lateral Overgrowth

Thursday, October 5, 2000, 3:20 pm, Room 306

Session: III-Nitride Growth and Nucleation
Presenter: M.E. Coltrin, Sandia National Laboratories
Authors: M.E. Coltrin, Sandia National Laboratories
C.C. Willan, Sandia National Laboratories
M.E. Bartram, Sandia National Laboratories
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Epitaxial Lateral Overgrowth (ELO) is a useful technique to improve material quality and reduce defects in GaN. In ELO, a mask pattern of dielectric material, usually either silicon nitride or silicon dioxide, is deposited on top of a GaN buffer layer. Further growth of GaN occurs selectively on exposed areas of the underlying buffer layer, and not on the dielectric material. Typically, ELO conditions are optimized for a maximum lateral - to - vertical growth rate ratio. Growth kinetics of GaN crystal faces and transport effects will be discussed in this paper. Dimensions of the exposed and masked areas in line and dot patterns, pattern orientation with respect to the underlying substrate, and growth time were systematically varied. Growth rate information was obtained from scanning electron microscope (SEM) measurements. The coupling between transport and kinetic effects was examined by means of 2-D and 3-D numerical simulations. In general, transport of material from the masked to the unmasked regions is quite efficient. However, ELO deposition growth efficiency is shown to decrease dramatically when the ratio of exposed to masked areas becomes very small. ELO experiments incorporating deep trenches will be described, which are designed to distinguish between lateral transport of material via gas-phase vs. surface diffusion. Gas-phase transport of material appears to dominate. We have found a quantitative way to translate results from different pattern dimensions into a pseudo time basis by scaling growth features by a length scale W, the size of the exposed deposition window.