The case for incorporating an arsenic capping layer in compound semiconductor device processing has been investigated with x-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED) and scanning electron microscopy (SEM). The As cap was found to be stable upon exposure to common processing chemicals, such as acetone, photoresist, developer, and N-methyl-2-pyrrolidone, a common polyimide solvent. A clean, c(4×4)-reconstructed GaAs(001) surface was recovered after thermal desorption of the cap in ultra-high vacuum, for a sample exposed to standard (maskless) photolithography. We also report a new technique for reactive decapping at room temperature, using a beam of hydrogen radicals (H*). Pattern definition in the As cap with ∼ 5 μm linewidth was demonstrated, using this technique. However, XPS and SEM data for the H*-etched specimens showed clear evidence of superficial gallium (sub)oxide and of As residues along the photoresist mask edges. This novel method of As cap patterning thus needs further refinement, before being useful to III-V device processing.