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A novel tellurium (Te) containing fluorophore, 1 and its nickel (2) and copper (3) containing metal organic complex (MOC) have been synthesized to exploit their structural and optical properties and to deploy these molecules as fluorescent probes for the selective and sensitive detection of picric acid (PA) over other commonly available nitro‐explosives. Furthermore, density functional theory (DFT) and single crystal X‐ray diffraction (SCXRD) techniques revealed the inclusion of "soft" Tellurium (Te) and "hard" Nitrogen (N), Oxygen (O) atoms in the molecular frameworks. Owing to the presence of electron rich "N" and "O" atoms along with "Te" in the molecular framework, 1 could efficiently and selectively sense PA with more than 80 % fluorescence quenching efficiency in organic medium and having detection limit of 4.60 μM. The selective detection of PA compared to other nitro‐explosives follows a multi‐mechanism based "turn‐off" sensing which includes photo‐induced electron transfer (PET), electrostatic (π‐π stacking and π‐anion/cation) interaction, intermolecular hydrogen bonding and inner filter effect (IFE). The test strip study also establishes the sensitivity of 1 for detection of PA. [ABSTRACT FROM AUTHOR]

We present a new analytical direct parameter-extraction methodology for obtaining the small-signal equivalent circuit of HBTs. It is applied to cryogenically operated SiGe HBTs as a means to allow circuit design of SiGe HBT low-noise amplifiers for cooled radio astronomy applications. We split the transistor into an intrinsic transistor (IT) piece modeled as a II-topology, and the quasi-intrinsic transistor (QIT), obtained from the IT after that the base resistance ([R.sub.b]) has been removed. The relations between Z-Y-parameters of the IT and QIT are then established, allowing us to propose a new methodology for determining lib. The present extraction method differs from previous studies in that each of the model elements are obtained from exact equations that do not require any approximations, numerical optimization, or post-processing. The validity of this new extraction methodology is demonstrated by applying it to third-generation SiGe HBTs operating at liquid-nitrogen temperature (77 K) across the frequency range of 2-22 GHz. Index Terms--Base resistance, cryogenic electronics, microwave SiGe HBTs, S-parameters, small-signal equivalent circuit.

A comprehensive investigation of the cryogenic performance of third-generation silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technology. The results demonstrate that aggressively scaled SiGe HBTs are inherently well suited for cryogenic electronics applications requiring extreme levels of transistor performance.

In this paper, we present a thermal analysis of AlGaN-GaN power heterojunction field-effect transistors (HFETs). We report the de, small-signal, large-signal, and noise performances of AlGaN-GaN HFETs at high temperatures. The temperature coefficients measured for GaN HFETs are lower than that of GaAs pseudomorphic high electron-mobility transistors, confirming the potential of GaN for high-temperature applications. In addition, the impact of thermal effects on the device de, small-signal, and large-signal characteristics is quantified using a set of pulsed and continuous wave measurement setups. Finally, a thermal model of a GaN field-effect transistor is implemented to determine design rules to optimize the heat flow and overcome self-heating. Arguments from a device, circuit, and packaging perspective are presented. Index Terms--AlGaN-GaN heterojunction field-effect transistors (HFETs), high temperature, microwave, thermal effect, thermal modeling.