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 etching (RIE) and a subsequent annealing process on AlGaAs/GaAs and pseudomorphic AlGaAs/InGaAs/GaAs heterostructures. We use low temperature Hall, Shubnikov-de Haas, and photoluminescence measurements. We observe that the electron density and mobility of the two-dimensional electron 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 annealing restores the electron mobility completely, for the AlGaAs/GaAs heterostructures the electron mobility recovers only to 60% of the original value. This indicates that in the AlGaAs/GaAs heterostructures the structural damage induced by reactive ion etching is not fully removed by thermal annealing. This is confirmed by photoluminescence measurements at low temperatures.