We evaluate the optical performance of the InP heterojunction bipolar transistors (DHBTs) designed for 100 Gbit/s circuit applications as a room temperature detector operating above 1 THz. They can operate far above the frequencies at which they have gain and can still rectify THz current and voltage.

Phenomena of the radiation coupling to the field effect transistors based terahertz detectors is studied. We show that in the case of flat metallic antennas important part of radiation, instead coupling to the transistors, is coupled to the substrate leading to losses. Experimental and theoretical investigations of the responsivity versus substrate thickness are performed. They clearly show how to minimize the losses by the detector substrate thinning.

A fully integrated 0.3 THz antenna-coupled plasma-wave detector with 10 GHz (measured) bandwidth is presented. Fabricated in 130nm CMOS technology, the chip is formed of an E-shaped patch antenna, plasmonic based Field Effect Transistor (FET) detector and a wide bandwidth amplifier employing inductive shunt peaking. The open drain mode of operation of the detector achieves an absolute responsivity of 10 V/W with a minimum signal to noise ratio (SNR) of 40 dB over the entire bandwidth. With a drain current of 0.24 mA, the responsivity increases by 10X with a decrease in bandwidth to 3 GHz. The detector is also characterized without the on chip amplifier for imaging applications and shows a measured absolute responsivity of 150 V/W for a drain current of 5 μA at 0.3 THz.

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.