For some dry etching applications in III-V semiconductors, such as via hole formation in InP substrates, the currently used plasma chemistries have etch rates that are too slow by up to a factor of 30. We report on the development of three new classes of discharge chemistries, namely C12-CH4-H2-Ar at 150 °C (yielding InP etch rates of greater than 1 pm min-1 at 1 mTorr and -80 V d.c.); HBr-H 2 for selective etching of InGaAs over AllnAs; and iodine-based plasmas (HI-H2, CH31-H2) that offer rapid anisotropic etching of all III-V materials at room temperature..In all cases electron cyclotron resonance sources (either multipolar or magnetic mirror) with additional r.f. biasing of the sample position are utilized to obtain low damage pattern transfer processes that generally use metal contacts on device structures as selfaligned etch masks. The temperature dependence of etch rates with these new chemistries display non-Arrhenius behavior in the range 50-250 °C and a detailed study of the phenomenon are reported. Electrical, optical and chemical analyses of the etched surfaces show that it is possible to achieve essentially damage-free pattern transfer.