We present a high‐resolution, damage‐free etching technique for GaAs and related compound semiconductors which utilizes surface‐specific photochemistry at 193 nm to excite a physisorbed layer of Cl2on a cryogenically cooled (∼140 K) sample. Etch rates as high as 0.25 Å/pulse (corresponding to 0.09 μm/min) have been achieved. Etching is anisotropic, and etched features of 0.2–0.3 μm linewidth have been routinely obtained. The etch rate has been characterized as a function of several ‘‘system’’ parameters including Cl2‐partial pressure, substrate‐temperature, laser repetition rate and fluence, and the addition of rare gases. A phenomenological model of this cryoetching has been developed which agrees well with the experimental data. The etch damage and contamination have been studied with Auger electron spectroscopy, photoluminescence, and Schottky‐barrier measurements. All results indicate that there is minimal if any damage induced by the cryoetching process.