Narrow Results

TeraFETs are THz power detectors based on field-effect transistors (FETs) integrated with antennas. The first part of this paper discusses the design of Si CMOS TeraFETs leading to an optimized noise-equivalent power close to the room-temperature limit. The impact of the choice of the gate width and gate length, the role of the parasitic effects associated with the technology node, and the conjugate matching of antenna and FET impedance – which is possible over narrow THz frequency bands because of the frequency dependence of the channel impedance resulting from plasmonic effects – are highlighted. Taking these aspects into account, we implement narrow-band detectors of two different designs. Using a 90-nm and a 65-nm CMOS technology, we reach a room-temperature cross-sectional NEP of 10 pW/√Hz at 0.63 THz. We then explore the optimization of AlGaN/GaN TeraFETs equipped with broadband antennae. A room-temperature optical NEP of 26 pW/√Hz is achieved around 0.5 THz despite the fact that the existence of pronounced ungated regions leads to a significant hot-electron thermoelectric DC voltage reducing the rectified signal. AlGaN/GaN TeraFETs become competitive and they have the added advantage that they are extraordinarily robust against electrostatic shock even without inclusion of protection diodes into the design.

It has been recently shown, that manufacturing p–n-junctions, field-effect and bipolar transistors, thyristors in a multilayer structure by diffusion or ion implantation under condition of optimization of dopant and/or radiation defects leads to increasing sharpness of p–n-junctions (both single p–n-junctions and p–n-junctions, which include into their system). In this situation, one can also obtain increase of homogeneity of dopant in doped area. In this paper, we consider manufacturing a field-effect heterotransistor without p–n-junction. Optimization of technological process with using inhomogeneity of heterostructure gives us possibility to manufacture transistors to be more compact.

We have measured the potential distribution on carbon nanotube (CNT) field-effect transistors (FETs) using electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KFM). Clearer potential profiles were obtained by EFM than by KFM. When the CNT-FET is in the ON state, the EFM image shows uniform potential distribution along the CNT. In contrast, when the CNT-FET is in the OFF state, nonuniform potential image with dark spots are obtained. The dark spots can be attributed to the defects in the CNTs.

The unipolar electron transport conjugated polymers play an important role in organic semiconductors. In this work, a unipolar electron transport polymer semiconductor was designed and synthesized based on fluorination on the donor unit and replacement of nitrogen on the acceptor unit. The optical properties, electrochemistry properties, and film morphology were systematically characterized and investigated. Heteroatom with large electronegativity could effectively lower the molecular orbital energy levels of conjugated polymer. Organic field-effect transistors (OFETs) devices were fabricated to investigate the charge transport properties. Unipolar electron transport characteristics were obtained with the highest field-effect mobility of over 0.03 cm²V${}^{-1}$s${}^{-1}$.

TeraFETs are THz power detectors based on field-effect transistors (FETs) integrated with antennas. The first part of this paper discusses the design of Si CMOS TeraFETs leading to an optimized noise-equivalent power close to the room-temperature limit. The impact of the choice of the gate width and gate length, the role of the parasitic effects associated with the technology node, and the conjugate matching of antenna and FET impedance – which is possible over narrow THz frequency bands because of the frequency dependence of the channel impedance resulting from plasmonic effects – are highlighted. Taking these aspects into account, we implement narrow-band detectors of two different designs. Using a 90-nm and a 65-nm CMOS technology, we reach a room-temperature cross-sectional NEP of 10 pW/√Hz at 0.63 THz. We then explore the optimization of AlGaN/GaN TeraFETs equipped with broadband antennae. A room-temperature optical NEP of 26 pW/√Hz is achieved around 0.5 THz despite the fact that the existence of pronounced ungated regions leads to a significant hot-electron thermoelectric DC voltage reducing the rectified signal. AlGaN/GaN TeraFETs become competitive and they have the added advantage that they are extraordinarily robust against electrostatic shock even without inclusion of protection diodes into the design.