Etch rates up to 7000 Angstrom/min for InP and 3500 Angstrom/min for GaAs are obtained for high microwave power (1000 W) CH4/H-2/Ar electron cyclotron resonance plasma etching. Preferential loss of the group V element leads to nonstoichiometric, unacceptably rough surfaces on In-based binary semiconductors at microwave powers greater than or equal to 400 W, regardless of plasma composition. Both Ga- and Al-based materials retain smooth, stoichiometric surfaces even at 1000 W but the rates are still much slower than for Cl-2 plasma chemistries. The results suggest that CH4/H-2 plasmas are not well suited to electron cyclotron resonance systems operating at high powers.