Backside-illuminated photoelectrochemical etching for the fabrication of deeply undercut GaN structures

A photoelectrochemical (PEC) wet-etching technique (backside-illuminated PEC) is described that utilizes the dopant or band-gap selectivity of PEC etching to fabricate deeply undercut structures. Lateral etch rates exceeding 5 mu m/min have been observed, producing cantilevers in excess of 100 mu m in length. Dramatically different etch morphologies were noted between the frontside- and backside-illuminated etching, though dopant-dependent etch selectivities were maintained. (C) 2000 American Institute of Physics. [S0003-6951(00)02542-0].