In this research, small self-assembled inverted hexagonal pyramids of GaN:Mg and InGaN/GaN multi-quantum-well (MQW) structures were formed using photoelectrochemical wet etching. We studied the formation mechanism of the pyramids during the etching process sequentially as lateral etching, bottom-up etching, and anisotropic etching. The (0001) Ga-face and {1011} faces were exposed to achieve the lowest possible surface energy. Due to the strain relief in the tips of the inverted nanopyramids with an MQW active region, an emission peak of photoluminescence with a strong blue shift of 252 meV was induced. (c) 2005 The Electrochemical Society.