A remarkable increase in InGaP etch rate in electron cyclotron resonance BCl3 discharges is observed as the microwave power is increased from 250 W (etch rate ∼500 A/min) to 1000 W (etch rate ∼8000 A/min). The surface roughness measured by atomic force microscopy decreases from 36 nm at 250 W to 2 nm at 1000 W. The high ion flux incident on the InGaP at high microwave powers appears to remove InClx species by sputter‐assisted desorption and prevents formation of the nonstoichiometric In‐rich surfaces generally observed with Cl2‐based dry etching using conventional reactive ion etching.