We investigate inductively coupled plasma deep dry etching of Al0.8Ga0.2As for photonic crystal (PC) fabrication using Cl2, BCl3, and CH4 chemistry. The characteristic AlO x deposition is observed during the etching, resulting in the reduction of etching rate. BCl3 is considered to scavenge the deposited AlO x by its reductive reaction. CH4 passivates the etching sidewall, as well as enhances the deposition of AlO x . Concerning the impact of pattern size, a pronounced inverse reactive ion etching (RIE) lag is observed, which is beneficial for small-size PC fabrication typically with a hole diameter of 100–500 nm. From the findings, we successfully fabricated a PC structure with air holes having an aspect ratio of 8 and a diameter of 110 nm.

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