Optical and infrared studies of [111] InGaAs/AlGaAs strained-layer superlattices

Low temperature far infrared magnetotransmission and near infrared magnetoreflectivity and photoluminescence measurements have been carried out on two [111] In_xGa_1-xAs/Al_yGa_1-yAs 70 A ̊ 140 A ̊ strained-layer superlattices (x∼0.1 and y=0. and ∼0.2). Hole cyclotron resonance was observed in both samples with effective masses of 0.068m_o and 0.113m_o for y=0 and y=0.2 respectively. Magnetoreflectivity spectra show features whose magnetic field dependence demonstrates their excitonic origin. A doublet structure observed in the reflectivity spectra for the y=0 superlattice is correlated with Landau-level-confinement-subband coupling experiments in a tilted magnetic field. Results provide direct evidence for the predicted large built-in electric fields in these novel structures.