Fabrication of GaN suspended microstructures

We report on a versatile processing technology for the fabrication of micro-electromechanical systems in gallium nitride (GaN). This technology, which is an extension of photo-electrochemical etching, allows for the controlled and rapid undercutting of p-GaN epilayers. The control is achieved through the use of opaque metal masks to prevent etching in designated areas, while the high lateral etch rates are achieved by biasing the sample relative to the solution. For GaN microchannel structures processed in this way, undercutting rates in excess of 30 μm/min have been attained. We propose two mechanisms to account for these high etch rates.