We report on Terahertz detection by inverted band structure HgTe-based Field Effect Transistor. Photoconductivity measurements allow for the observation of cyclotron resonance and Shubnikov-de-Haas-like oscillations. However, an unexpected peak was observed at the critical magnetic field value for which zero mode Landau Levels are crossing. Therefore, this specific feature of TeraHertz photoconductivity spectra can tentatively attributed to this magnetic field driven topological phase transition.

We report terahertz measurements on bulk HgCdTe crystals at the semiconductor- to-semimetal topological transition and InAs/GaSb inverted band structure quantum well. We show that physical parameters of these narrow gap systems driven in specific topological phases can be efficiently extracted by means of terahertz photoconductivity studies.

This paper presents terahertz detectors based on high performance 0.7-μm InP double heterojunction bipolar transistor (DHBT) technology and reports on the analysis of their voltage responsivity over a wide frequency range of the incoming terahertz radiation. The detectors operated without any spatial antennas to couple terahertz radiation to the device and have been characterized in the 0.25 - 3.1 THz range with the responsivities (normalized to 1 W radiant power) of 5 V/W and 200 μV/W measured at 0.35 THz and 3.11 THz, respectively. The InP DHBTs also performed as the imaging single-pixels at room temperature in the raster scanned transmission mode. A set of the sub-terahertz images of plant leaves suggest potential utility of InP DHBT detectors for terahertz imaging dedicated to non-invasive testing of plants.

We report on terahertz photoconductivity under magnetic field up to 16 T of field effect transistor based on HgTe quantum well (QW) with an inverted band structure. We observe pronounced cyclotron resonance and Shubnikov-de Haas-like oscillations, indicating a high mobility electron gas in the transistor channel. We discover that nonlinearity of the transistor channel allows for observation of characteristic features in photoconductivity at critical magnetic field corresponding to the phase transition between topological quantum spin Hall and trivial quantum Hall states in HgTe QW. Our results pave the way towards terahertz topological field effect transistors.

We report on sub-Terahertz photoconductivity of bulk HgxCd1-xTe crystals withcomposition close to semiconductor-to-semimetal topological transition. Low magnetic fieldShubnikov-de Hass like oscillations were observed with a period which does not depend onthe incident frequency. Moreover, anomalous B-periodic oscillations were also observed athigher magnetic fields.

Light scattering spectroscopy, mainly developed for Cu(In,Ga)Se2 thin films growth, has been demonstrated to be an efficient in-situ monitoring tool. It consists of illuminating the substrate surface using a light source and collecting the diffused light with a spectrometer. The on-line information allows monitoring the point of stoichiometry of the grown layer. In this work, we propose an alternative approach of this method, replacing the spectrometer by a standard webcam. This system allows to precisely choose the analyzed area on the substrate surface, which may be the whole sample surface or just a specific zone. We have grown CuInSe2 (CIS) thin films by co-evaporation under vacuum using the three-stage process. We have simultaneously performed CIS growth on both Mo-coated and bare glass substrates within the same growth run, while, on purpose, the scattered light was collected from the Mo-coated substrate. The CIS thin films were characterized by X-ray diffraction, atomic force microscopy, Hall effect measurements, absorption spectroscopy and energy dispersive spectroscopy for composition. By interrupting the CIS growth at different stages of the growth process, we have correlated the scattered light features with the Cu-rich/In-rich transitions and we observe the reproducibility of the scattered light spectra structures.