We have investigated the compatibility of Cl-2/BCl3/IBr3 etch gas mixtures with a cryo-pumped ultrahigh vacuum chemically assisted ion-beam etching system. The machine was designed for the fabrication of ultrahigh-quality laser facets in monolithically integrated GaAs- and InP-based optoelectronic integrated circuits. The chemical composition of etch byproducts deposited in the vacuum chambers and the pumping system has been examined in particular detail. After 70 h of process time, samples of such deposits were scraped from the chamber walls and the various stages of the cryo-pump and roughing pump; these samples were analyzed using energy-dispersive x-ray measurements. Automated overnight regeneration of the cryopump, the use of integrated external bakeout heaters, and the implementation of a cryo-pumped load-lock chamber allow the deposition of reactive Cl-containing residues to be confined to surfaces and components which can be cleaned or replaced during routinely scheduled yearly maintenance.