Reactive ion etching damage to GaAs layers with etch stops

The reactive ion etching damage occurring in GaAs/AlGaAs heterostructure devices etched in CCl2F2 and He at low-self-bias voltages (−85 V) was characterized by Schottky diodes. The effect of overetching was examined by etching down to a thin AlAs etch stop layer and electrically characterizing the underlying GaAs layers. Simultaneously etched bulk samples displayed less damage, indicating that bulk samples may not give a true indication of the damage in heterojunction samples. It was deduced that helium ions are most probably responsible for the damage observed.