The etch rates of InGaP, AlInP and AlGaP increases dramatically with microwave power in ECR BCl3- or CH4/H2-based discharges, reaching values near 1μm·min−1 at 1000W, The surface morphologies of these materials however behave much differently as the microwave power is increased. For BCl3 etching of InGaP the surface RMS roughness decreases from 36nm at 250W to 2nm at 1000W. For AlInP, there is little change in surface morphology, whereas for the common binary component of these two materials, InP, the surface becomes very rough at high powers (>60nm RMS). By contrast, the morphologies of the three ternaries remain smooth over a wide range of conditions with CH4/H2/Ar. The AFM analysis, coupled with AES enables us to understand these different responses in terms of volatility of the respective chloride, metalorganic and hydride etch products.