Selective photochemical etching of GaN films and laser lift-off for microcavity fabrication

Wavelength dependent photochemical etching of GaN films reveals strong dependence of the photocurrent on the excitation wavelength. Sharp increase in the photocurrent with increasing photon energy is attributed to the onset of absorption above the GaN bandgap. The etching rate of GaN films strongly correlates with the measured photocurrent. No photocurrent and etching is observed for AlGaN films under same conditions. The method could pave the way to the development of truly selective self‐stop etching of GaN on AlGaN yielding smooth surfaces for the fabrication of GaN based microcavities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)