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

Abstract

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 〈〉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 × 107 cm−2 and the c-axis tilt angle was 0.19°.