The etch rate of GaAs and AIGaAs during CC12F2:O2 reactive ion etching was measured over the temperature range 50–400ºC. For GaAs, the etch rate increases super-linearly from ∼400Å.min−1 to ∼3000Åmin−1 over this temperature range for a 0.56 W.cm−2, 4 mTorr discharge with a 19:1 CC12F2:O2 mixture. The surface morphology of GaAs undergoes a smooth-to-rough transition near 150ºC, and theresidual damage in the near-surface region appears to decrease with increasing etch temperature. The I-V characteristics of Schottky diodes fabricated on the etched surfaces show ideality factors of 1.001 for 150ºC RIE, although these worsen because of thermal degradation of higher etching temperatures. From AES and XPS data the etched GaAs shows little contamination after etching. In contrast, little temperature dependence of the etch rate of AIGaAs is observed using CC12F2:O2, although once again there is surface degradation for etching temperatures above 150ºC.