We report on temperature-dependent terahertz spectroscopy of a three-layer InAs/GaSb/InAs quantum well (QW) with inverted-band structure. The interband optical transitions, measured up to 16 T at different temperatures by Landau-level magnetospectroscopy, demonstrate the inverted-band structure of the QW. The terahertz photoluminescence at different temperatures allows us to directly extract the optical gap in the vicinity of the Γ point of the Brillouin zone. Our results experimentally demonstrate that the gap in the three-layer QWs is temperature independent and exceeds by four times the maximum band gap available in the inverted InAs/GaSb bilayers.

We report a direct observation of temperature-induced topological phase transition between trivial and topological insulator in HgTe quantum well. By using a gated Hall bar device, we measure and represent Landau levels in fan charts at different temperatures and we follow the temperature evolution of a peculiar pair of "zero-mode" Landau levels, which split from the edge of electron-like and hole-like subbands. Their crossing at critical magnetic field Bc is a characteristic of inverted band structure in the quantum well. By measuring the temperature dependence of Bc, we directly extract the critical temperature Tc at which the bulk band-gap vanishes and the topological phase transition occurs. Above this critical temperature, the opening of a trivial gap is clearly observed.

An electromagnetic wave detector comprises a field effect transistor, an antenna 601 connected to a first end of a gate 608 of the field effect transistor for receiving incident electromagnetic waves, and a biasing connection pad 605 connected to a second end of the gate 608 for applying a bias voltage to the transistor. The antenna may have a first part 601b connected to the first end of the gate 608 and a second part 601a connected to a source 602 of the transistor. The detector may further comprise a virtual ground element 607 connected to the second end of the gate 608. A control module may control the bias voltage applied on the biasing connection pad 605 according to the electromagnetic power received by the detector. The transistor may be a high electron mobility transistor (HEMT).

At least one electronic device, system and method of manufacturing an electromagnetic wave detector are provided herein. The electronic device for receiving at least one electromagnetic wave of a given frequency may comprise at least one first field effect transistor, and at least one antenna configured to receive the at least one electromagnetic wave and connected to a gate of the at least one first field effect transistor, wherein a length of the gate is in a same order of magnitude as an oscillation length of an oscillation regime of the at least one first field effect transistor at the given frequency, and a width of the gate is such that an impedance presented by the at least one first field effect transistor in the oscillation regime is adapted to an impedance of the at least one antenna.

We report on the photoresponse of 0.7-μm InP double heterojunction bipolar transistor to THz radiation of low and high intensities, when the collector is unbiased. At low intensities, the photoresponse is linear in radiation intensity. Under intense laser radiation, we observe a saturation at intensities > 15 kW/cm2, sample damaging arising around ∼ 40 kW/cm2. The photoresponse as a function of base-emitter bias dependence does not change with the radiation intensity.

We have evaluated the performance of the InP double heterojunction bipolar transistor and InP-based varactors as a room temperature sensitive detectors for THz computed tomography applications. They were used in transmission mode for the 350 GHz and 650 GHz atmospheric windows.