We have developed an inductively coupled plasma etching process for fabrication of high-aspect-ratio hole-type photonic crystals in InP, which are of interest for optical devices involving the telecommunication wavelength of 1550 nm. The etching was performed at 250 degrees C using Cl-2/O-2 chemistry for sidewall passivation. The process yields nearly cylindrical features with an aspect ratio larger than 10 for hole diameters near 0.25 mu m. This makes them very suitable for high-quality photonic crystal patterns. (c) 2006 American Vacuum Society.