Electron concentration and mobility loss in GaAs/GaAlAs heterostructures caused by reactive ion etching

We have investigated the influence of reactive ion etching on the properties of a two-dimensional electron gas in GaAs/GaAlAs heterostructures at 4.2 K. After removing the GaAs cap layer and overetching on the surface of the n-GaAlAs with CCl2F2 under various etching conditions we observe both a reduction of the electron concentration and a low-field mobility loss which are correlated with ion energy. We ascribe this mobility loss to a capture of electrons into traps created by the etching process. Ion energies around 25 eV were found to meet best the requirements for low damaging as well as anisotropic etching, whereas energies exceeding 35 eV result in a complete depletion of the two-dimensional electron gas.