Dry etching of GaAs in asymmetric bipolar pulsed dc BCl3 plasmas using only mechanical pumping is reported. The mean pulsed dc voltage on the cathode was used as a process variable in the experiment. When the mean pulsed dc voltage changed from −350 to −550 V at the cathode electrode, the dependent mean current and power were increased from 0.22 to 0.33 A and from 100 to 220 W, respectively. The etch rate of GaAs increased from 0.01 to 0.55 μm/min, and etch selectivity over photoresist was also strongly increased from 0.2:1 to 2.2:1 with this voltage change. The threshold mean voltage for plasma ignition pulsed dc plasma was −350 V. Scanning electron microscopy micrographs showed that dry etching at −500 V provided excellent surface smoothness (rms roughness of ∼1 nm) and sidewall passivation. At a lower mean voltage of −400 V, there was a rough surface and some undercutting of GaAs after etching at −400 V. Degradation of the photoresist surface was negligible in both cases.