TRANSPORT AND OPTICAL-PROPERTIES OF ALGAAS GAAS AND PSEUDOMORPHIC ALGAAS/INGAAS/GAAS HETEROSTRUCTURES SUBJECTED TO CH4/H2 REACTIVE ION ETCHING/

We investigate the effect of methane/hydrogen (CH4/H-2) reactive ion e tching (RIE) and a subsequent annealing process on AlGaAs/GaAs and pse udomorphic AlGaAs/InGaAs/GaAs heterostructures. We use low temperature Hall, Shubnikov-de Haas, and photoluminescence measurements. We obser ve that the electron density and mobility of the two-dimensional elect ron gas in the heterostructure is strongly reduced by the RIE process. After annealing the electron density fully recovers for both types of structures, whereas the electron mobility responds differently. While for the pseudomorphic AlGaAs/InGaAs/GaAs heterostructures thermal ann ealing restores the electron mobility completely, for the AlGaAs/GaAs heterostructures the electron mobility recovers only to 60% of the ori ginal value. This indicates that in the AlGaAs/GaAs heterostructures t he structural damage induced by reactive ion etching is not fully remo ved by thermal annealing. This is confirmed by photoluminescence measu rements at low temperatures.