Fabrication of deeply undercut GaN-based microdisk structures on silicon platforms

The authors demonstrate the use of a dry releasing technique to achieve deeply undercut GaN-based microdisk structures supported by silicon platforms. Varying dimensions of microdisk structures on silicon posts with large air gaps are fabricated by a $XeF2$-based dry etching of the underlying silicon material. The residual stress variation in these microdisks is studied by high spectral resolution micro-Raman mapping. Such a fabrication technique may effectively improve the light extraction efficiency from GaN-based microdisk light emitting diodes on silicon substrates.