The influence of in situ argon cleaning of GaAs on the electrical characteristics of Schottky diodes and metal–semiconductor field-effect transistors (MESFETs) is investigated. The beam energy was varied from 50 to 500 eV and the characteristics were compared to wet chemically cleaned devices. The characteristics of the Schottky diodes showed a significant degradation as a consequence of damage introduced by argon cleaning. Recovery was obtained with an additional annealing step at 300¿°C for diodes cleaned at energies below 125 eV. For higher energies, the samples became worse with annealing. MESFETs showed degraded performances for positive gate voltages due to a high gate leakage current. Improvement was also obtained upon annealing.