Highly Reflective GaN-Based Air-Gap Distributed Bragg Reflectors Fabricated Using AlInN Wet Etching

We report the fabrication of four-period GaN-based air-gap distributed Bragg reflectors (DBRs) using wet etching of sacrificial AlInN layers. The epitaxial structure grown by Molecular Beam Epitaxy consists of four GaN/Al0.83In0.17N pairs. The sacrificial AlInN layers are selectively under-etched in hot nitric acid to form the air-gap DBR in micro-bridges. Micro-reflectivity spectra exhibiting flat and well defined stop-bands are observed, with peak reflectivities >99% at 590 nm and ~74% at 400 nm. The full-width half maximum of the widest stop-band is 170 nm in agreement with transmission matrix simulations. Such devices are robust and offer an attractive basis for GaN-based microlasers and microcavities.