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AlGaN/GaN high-electron-mobility transistors (HEMTs) with postpassivation plasma treatment are demonstrated and investigated for the first time. The results show that postpassivation plasma treatment can reduce the gate leakage and enhance the drain current. Comparing with the conventional devices, the gate leakage of AlGaN/GaN HEMTs with postpassivation plasma decreases greatly while the drain current increases. Capacitance–voltage measurement and frequency-dependent conductance method are used to study the surface and interface traps. The mechanism analysis indicates that the surface traps in the access region can be reduced by postpassivation plasma treatment and thus suppress the effect of virtual gate, which can explain the improvement of DC characteristics of devices. Moreover, the density and time constant of interface traps under the gate are extracted and analyzed. [ABSTRACT FROM AUTHOR]

In this paper, two-dimensional (2D) transient simulations of an AlGaN/GaN high-electron-mobility transistor (HEMT) are carried out and analyzed to investigate the current collapse due to trapping effects. The coupling effect of the trapping and thermal effects are taken into account in our simulation. The turn-on pulse gate-lag transient responses with different quiescent biases are obtained, and the pulsed current–voltage (I–V) curves are extracted from the transients. The experimental results of both gate-lag transient current and pulsed I–V curves are reproduced by the simulation, and the current collapse due to the trapping effect is explained from the view of physics based on the simulation results. In addition, the results show that bulk acceptor traps can influence the gate-lag transient characteristics of AlGaN/GaN HEMTs besides surface traps and that the thermal effect can accelerate the emission of captured electrons for traps. Pulse transient simulation is meaningful in analyzing the mechanism of dynamic current collapse, and the work in this paper will benefit the reliability study and model development of GaN-based devices. [ABSTRACT FROM AUTHOR]

In this paper, we explore the technology of tracking a group of targets with correlated motions in a wireless sensor network. Since a group of targets moves collectively and is restricted within a limited region, it is not worth consuming scarce resources of sensors in computing the trajectory of each single target. Hence, in this paper, the problem is modeled as tracking a geographical continuous region covered by all targets. A tracking algorithm is proposed to estimate the region covered by the target group in each sampling period. Based on the locations of sensors and the azimuthal angle of arrival (AOA) information, the estimated region covering all the group members is obtained. Algorithm analysis provides the fundamental limits to the accuracy of localizing a target group. Simulation results show that the proposed algorithm is superior to the existing hull algorithm due to the reduction in estimation error, which is between 10% and 40% of the hull algorithm, with a similar density of sensors. And when the density of sensors increases, the localization accuracy of the proposed algorithm improves dramatically. [ABSTRACT FROM AUTHOR]

A unified charge-based model for fully depleted silicon-on-insulator (SOI) metal-oxide semiconductor field-effect transistors (MOSFETs) is presented. The proposed model is accurate and applicable from intrinsic to heavily doped channels with various structure parameters. The framework starts from the one-dimensional Poisson-Boltzmann equation, and based on the full depletion approximation, an accurate inversion charge density equation is obtained. With the inversion charge density solution, the unified drain current expression is derived, and a unified terminal charge and intrinsic capacitance model is also derived in the quasi-static case. The validity and accuracy of the presented analytic model is proved by numerical simulations. [ABSTRACT FROM AUTHOR]

This paper proves that a set of orthogonal pure states are indistinguishable by restricted local projective measurement and classical communication if the sum of their Schmidt ranks is larger than the dimension of their joint Hilbert space. This result is useful in determining the local distinguishability of quantum states and is stronger in some respects than that of Hayashi et al [Phys. Rev. Lett. 96, 040501]. In addition, it presents a new method to determine the local distinguishability of orthogonal states by projecting measurement operators into their subspaces. [ABSTRACT FROM AUTHOR]

We generalize BB84 quantum key distribution (QKD) to the scenario where the receiver adopts a heralded quantum memory (QM). With the heralded QM, the valid dark count rate of the receiver's single photon detectors can be mitigated obviously, which will lower the quantum bit error rate, and thus improve the performance of decoy-state BB84 QKD systems in long distance range. Simulation results show that, with practical experimental system parameters, decoy-state BB84 QKD with QM can exhibit performance comparable to that of without QM in short distance range, and exhibit performance better than that without QM in long distance range. [ABSTRACT FROM AUTHOR]

In this study rectangular AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with 22-nm and 12-nm AlGaN barrier layers are fabricated, respectively. Using the measured capacitance–voltage and current–voltage characteristics of the prepared devices with different Schottky areas, it is found that after processing the device, the polarization Coulomb field (PCF) scattering is induced and has an important influence on the two-dimensional electron gas electron mobility. Moreover, the influence of PCF scattering on the electron mobility is enhanced by reducing the AlGaN barrier thickness. This leads to the quite different variation of the electron mobility with gate bias when compared with the AlGaN barrier thickness. This mainly happens because the thinner AlGaN barrier layer suffers from a much stronger electrical field when applying a gate bias, which gives rise to a stronger converse piezoelectric effect. [ABSTRACT FROM AUTHOR]

We report the optical response characteristics of Al/Ti bilayer transition edge sensors (TESs), which are mainly comprised of Al/Ti bilayer thermometers and suspended SiN membranes for thermal isolation. The measurement was performed in a 3He sorption refrigerator and the device's response to optical pulses was investigated using a pulsed laser source. Based on these measurements, we obtained the effective recovery time (τeff) of the devices at different biases and discussed the dependence of τeff on the bias. The device with a 940 μm × 940 μm continuous suspended SiN membrane demonstrated a fast response speed with τeff = 3.9 μs, which indicates a high temperature sensitivity (α = T/R · dR/dT = 326). The results also showed that the TES exhibits good linearity under optical pulses of variable widths. [ABSTRACT FROM AUTHOR]