Low-dislocation density AlGaN layer by air-bridged lateral epitaxial growth

A high quality AlGaN layer with low dislocation density and low c-axis tilt angle in wing regions was demonstrated by the advanced ELO technique, namely air-bridged lateral epitaxial growth. An underlying GaN seed layer was grooved along the <1 (1) under bar 00>(GaN) direction to the sapphire substrate, whose sidewalls and etched bottoms were covered with silicon nitride masks, and regrowth of AlGaN was carried out by a low-pressure metalorganic vapor phase epitaxy system. Fabrication of air-bridged structures suppresses interference of nucleated poly-crystals on the silicon nitride masks during lateral growth, and the low dislocation density AlGaN layer was realized. The threading dislocation density in the wing regions was reduced to 2 x 10(7) cm(-2) and the c-axis tilt angle was 0.19degrees. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.