A high-quality AlGaN layer, with a low dislocation density and a low c-axis tilt angle in the wing regions, was obtained by air-bridged lateral epitaxial growth. An underlying GaN seed layer was grooved along the <1¯1▪0>GaN direction to the sapphire substrate, whose side-walls and etched bottoms were covered with silicon nitride masks, and re-growth of AlGaN was carried via low-pressure metalorganic vapor phase epitaxy. The fabrication of air-bridged structures suppressed interference from polycrystals nucleated on the silicon nitride masks during lateral growth, and a low dislocation density AlGaN layer was obtained. The threading dislocation density in the wing regions was reduced to 2 x 107/cm2, while the c-axis tilt angle was 0.19°.

Low Dislocation-Density AlGaN Layer by Air-Bridged Lateral Epitaxial Growth. Y.Kawaguchi, G.Sugahara, A.Mochida, T.Shimamoto, A.Ishibashi, T.Yokogawa: Physica Status Solidi C, 2003, 0[7], 2107-10