Microstructural Characterization of Semipolar GaN Templates and Epitaxial-Lateral-Overgrown Films Deposited on $M$-Plane Sapphire by Metalorganic Vapor Phase Epitaxy

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The microstructure of GaN templates and epitaxial lateral overgrown (ELO) films deposited on $M$-plane sapphire is investigated by transmission electron microscopy. The epitaxial relationship is $[11\bar{2}0]_{\text{sapphire}}\parallel[1\bar{1}00]_{\text{GaN}}$ in-plane with a growth plane close to $(11\bar{2}2)_{\text{GaN}}$. The microstructure of the templates is dominated by the presence of basal stacking faults with a density of around $3\times 10^{5}$ cm-1. Basal stacking faults are either terminated by partial dislocations or connected by prismatic stacking faults. Perfect dislocations are also observed. ELO films with stripes parallel to $[1\bar{1}00]_{\text{GaN}}$ allow us to reduce the density of basal stacking faults in the overgrown regions down to $5\times 10^{3}$ cm-1. In these overgrown materials, the density of perfect dislocations is $10^{8}$ cm-2 while neither partial dislocation nor prismatic stacking faults are observed.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2007-07-15