Effect of Misorientation Angle of $r$-Plane Sapphire Substrate on $a$-Plane GaN Grown by Metalorganic Vapor Phase Epitaxy

概要

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We investigated the effect of the misorientation angle of an $r$-plane sapphire substrate on $a$-plane GaN grown by metalorganic vapor phase epitaxy. The misorientation angle was changed systematically in the direction of the [0001] $c$-axis or [$\bar{1}100$] $m$-axis (denoted $\theta 1$) and in the direction of the [$11\bar{2}0$] $a$-axis (denoted $\theta 2$). Results show that the surface morphology and crystalline quality are very sensitive to $\theta 1$ misorientation angle. We successfully grew an $a$-plane GaN layer with a pit-free surface by optimizing the misorientation angle of the $r$-plane sapphire substrate. We found that the $r$-plane sapphire substrate with a $\theta 1$ misorientation angle between $-0.53$ and $-0.28$° is very effective for growing $a$-plane GaN with a pit-free surface. Moreover, a $\theta 1$ misoriention angle between $-0.53$ and $-0.28$° improves crystalline quality in the GaN $c$-axis direction, but causes a slight increase in tilt mosaicity in the GaN $m$-axis direction. In contrast, a $\theta 2$ misorientation angle between $-0.55$ and +0.52° produces no differences in the surface morphology and crystalline quality of $a$-plane GaN.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2008-01-25