Electron cyclotron resonance (ECR) plasma etch processes with CH4/H-2/Ar have been investigated on different III-V semiconductor materials (GaAs, AlGaAs, InGaAs, and InP). The passivation depth as a function of the GaAs carrier concentration and the recovery upon annealing at different temperatures have been determined by C-V measurements. Little degradation on the characteristics of Schottky diodes is observed with increasing process biases. If the GaAs top layer of an AlGaAs/GaAs heterostructure is removed by plasma processing the Hall mobility is restored to 74% after annealing at 425 degrees C. This is compared to a wet chemically etched reference sample. The 2-DEG sheet density fully recovers. However, if an Si delta-doped layer is incorporated in the heterostructure the Hall mobility and the sheet density completely restore after plasma etching and subsequent annealing. In the experiments minimal damage is observed at a substrate bias of -40 V. The direct current and high frequency characteristics of a dry and wet etched pseudomorphic heterostructure field-effect transistors are compared.