Photoelectrochemical undercut etching for fabrication of GaN microelectromechanical systems

The authors have developed a wet, band-gap-selective, photoelectrochemical etching process capable of producing cantilever microelectromechanical systems from InGaN/GaN heterostructures. Fabricated cantilevers were successfully actuated, and resonance spectra were measured. The as-grown strain gradient in the GaN film was found to relax upon removal, resulting in upward curvature of the cantilevers. This curvature was shown to be reversible with the integration of strained InGaN layers on the top surface of the cantilever. All photoelectrochemical wet etching was conducted using a benchtop lamp-and-filter arrangement, employing GaN and InGaN films as filters.