We report on the etching characteristics of GaAs and AlGaAs in capacitive BCl3/SF6 plasmas modulated at a pulse timing of a few milliseconds. Under such conditions, we obtained GaAs etch rates in the 0.25 mu m min(-1) range, with selectivities over AlGaAs of similar to 100. The effects of plasma-induced damage to GaAs were also measured by diode ideality factor and barrier height measurements. The electrical characteristics of the diodes show less prominent dry etch damage than in the continuous reactive ion-etching conditions, a promising result for optimized gate recess in the fabrication of AlGaAs/GaAs high-electron-mobility transistors. (c) 2007 The Electrochemical Society.