Abstract
Summary form only given. The results of measurements on photon-assisted tunnelling in triple-barrier quantum well structures are reported. The series of AlGaAs/GaAs structures have been extensively characterised and have quantum well confinement energies of 40 to 90 meV. The energy width of the quantum well states is appropriately 1.2 meV. A Cavendish Laboratory quantum cascade laser (2.9 THz, >50 mW) excites transitions between quantum wells when the first well is thermally populated and the correct separation of the quantum well states has been achieved by the applied bias. The electromagnetic field is coupled into the structures by metallic diffraction gratings with periods between 15 and 29 /spl mu/m. The photo-induced currents have been measured as a function of bias and temperature. The estimated detectivities are compared with those for other Terahertz detectors. The potential for improvement in detectivity by optimizing the coupling of the electromagnetic field into the structures is discussed.
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