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Photoelectrochemical (PEC) etching is a rapid and inexpensive means of etching GaN, InGaN, and related materials for micro-electro-mechanical systems (MEMS) applications. In this work, we show that bandgap engineering of GaN/InGaN heterostructures can be used to exert substantial control over PEC etching and achieve strain-free cantilevers. A single, 200-nm thick layer InGaN was selectively etched using bandgap-selective PEC etch. We show that the use of highly doped guard layers to confine photogenerated holes uniformly across the InGaN layer enables a uniform, fast, and effective PEC etch. This approach enables complete uniform etching using PEC and could enable many optical and MEMS devices. [ABSTRACT FROM AUTHOR]