Fabrication and spectroscopy of GaN microcavities made by epitaxial lift-off

A novel epitaxial lift-off process for III-nitrides, involving selective removal of a sacrificial (Al, In)N layer in a hot nitric acid etchant, is reported. This was applied to the fabrication of 1−λ GaN planar microcavities bounded by two dielectric DBRs, starting from epitaxial GaN-(Al, In)N-GaN trilayers grown on free-standing GaN or high-quality GaN template material. An optically smooth surface was retained on the GaN surface exposed to the nitric acid etch, with root mean square roughness values as low as 2 nm over 8 μm×8 μm areas. Photoluminescence and reflectivity spectra were recorded from completed microcavities, and the latter showed clear dips in the region of 3.5 eV.