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In this work, the single-event burnout (SEB) mechanism of p-GaN gate AlGaN/GaN HEMTs has been studied systematically. The irradiation experiment was carried out based on Ta ions with high linear energy transfer of 75.4 MeV/(mg/cm2), a standard criterion for commercial space applications. It is clearly observed that both the drain current and gate current increase during the irradiation. With the increasing drain bias, the device burns out eventually. Technology computer-aided design simulation was used to explore the possible burnout mechanism. The local high electric field peak induced by the electron and hole redistribution was proposed to explain the permanent damage. When heavy ions impact the device, electron–hole pairs are formed. With the aid of a horizontal electric field across the channel, electrons and holes move toward the drain and gate, respectively. The accumulation of electrons and holes around the drain edge and gate edge induces the local high electric field, which is even higher than the intrinsic breakdown electric field of GaN and AlGaN. The scanning electron microscope results verified the proposed SEB mechanism. This research offers significant theoretical and experimental insights for evaluating the reliability of GaN power devices against high-energy single-event burnout in aerospace applications. [ABSTRACT FROM AUTHOR]

The synergistic impact of reverse bias stress and 3 MeV proton irradiation on the β-Ga2O3 p–n diode has been studied from the perspective of the defect in this work. The forward current density (JF) is significantly decreased with the increase in proton irradiation fluence. According to the deep-level transient spectroscopy results, the increase in the acceptor-like trap with an energy level of EC-0.75 eV within the β-Ga2O3 drift layer, which is most likely to be Ga vacancy-related defects, can be the key origin of the device degradation. The increase in these acceptor-like traps results in the carrier concentration reduction, which in turn leads to a decrease in JF. Furthermore, compared with the case of proton irradiation with no bias, the introduction of −100 V electrical stress induced a nearly double decrease in JF. Based on the capacitance–voltage (C–V) measurement, with the support of the electric field, the carrier removal rate increased from 335 to 600 cm−1. Similar to the above-mentioned phenomenon, the trap concentration also increased significantly. We propose a hypothesis elucidating the synergistic effect of electrical stress and proton irradiation through the behavior of recoil nuclei under the electric field. [ABSTRACT FROM AUTHOR]

In this Letter, a single-event burnout (SEB) mechanism in gallium nitride (GaN) microwave monolithic integrated circuit power amplifiers with a high linear energy transfer of 78.1 MeV·cm2/mg has been investigated in detail. A typical SEB phenomenon was observed. With the aid of photon emission measurements and scanning electron microscopy, it is found that catastrophic burnout occurs in the power-stage GaN high electron mobility transistors (HEMTs) and the metal–insulator–metal (MIM) capacitors, respectively. For the GaN HEMT, the incident heavy ions will generate electron–hole pairs within it, which can gain enough energy with the transverse high electric field. The high-energy electrons will collide with the lattice near the drain electrode and induce significant electron trapping, which will result in a significant longitudinal local electric field. When a critical electric field is achieved, catastrophic burnout occurs. For the MIM capacitor, the burnout is attributed to the single-event dielectric rupture via severe impact ionization or latent tracks when heavy ions strike it. [ABSTRACT FROM AUTHOR]

Multi-level cell storage technology based on resistive random access memory (RRAM) with multi-level state characteristics is more attractive in achieving low-cost ultra-high-density nonvolatile memory. Although a large number of literatures have reported the multi-level state characteristics of RRAM, so far there is no unified model that can well explain the intrinsic reasons for the existence of intermediate resistance state (IRS) and the switching mechanism between different resistance states. Multi-level state characteristics are observed by I–V characteristic measurements on RRAM with TiN/HfOx/barrier layer/TiN stacks fabricated using a commercialized 28 nm CMOS process. Compared to other published resistive switching models, the proposed model based on trap-assisted tunneling is more consistent with the measured. The model can reproduce the multi-level state characteristics based on the mechanism that interaction between defects and oxygen vacancies at the interface of HfOx and TiN electrode, resulting in the formation of multiple weak conductive filaments. Furthermore, the wide spread of high resistance state (HRS) and the switching between HRS and IRS are determined by the distance of tunneling gap. As HfOx-based RRAM will soon be commercialized, it is becoming very urgent to clarify the switching mechanisms of multi-level state characteristics and propose a universal model. Consequently, this work satisfied the current demand and significantly advanced the understanding and development of commercialized, cost-effective, high-density multi-bit HfOx-based RRAM technology. [ABSTRACT FROM AUTHOR]

In this Letter, threshold voltage instability of p-GaN gate AlGaN/GaN HEMTs under high-temperature reverse bias (HTRB) stress has been investigated in detail. The experimental results show that the threshold voltage increases by 0.62 V after 100 ks stress at 200 °C. Especially, the degradation phenomenon is unrecoverable. A deep-level transient spectroscopy (DLTS) technique is used to characterize the defect evolution process during the stress. Two kinds of electron traps within the p-GaN layer were proposed to explain the degradation, which were generated by the injected high-energy electrons from the gate electrode. One is referred to as fixed charge trap, and another is trap E3 (EC-0.7 eV). With the aid of high temperature, more electrons are injected and trapped in the fixed charge trap, which causes the permanent threshold voltage increase. In addition, the concentration and capture cross section of trap E3 were extracted as well, which are considered to dominate the recoverable degradation of the device due to the relatively shallower energy level. [ABSTRACT FROM AUTHOR]

This paper is concerned with the pathwise dynamics of a class of stochastic discrete complex Ginzburg–Landau equations with long-range interactions. Under suitable assumptions on the weight function and coupling parameters of long-range interactions, we prove the existence and uniqueness of the random attractor for the considered system in weighted space. [ABSTRACT FROM AUTHOR]

This paper is concerned with the stationary approximations of the stochastic wave equations defined on R n with critical exponents. For a class of nonlinear diffusion terms, we prove the existence and uniqueness of tempered pullback attractors of the random wave equations driven by a stationary process as an approximation to the white noise. For a linear multiplicative noise, we prove the upper semicontinuity of these attractors as the step size of the approximations approaches zero. The asymptotic compactness of the solutions on R n is established by the idea of energy equations and the uniform estimates on the tails of the solutions. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Wong–Zakai approximations and random attractors for stochastic discrete complex Ginzburg–Landau equations driven by nonlinear multiplicative noise. We establish the existence of the random attractor for the approximate system. For linear multiplicative noise or additive noise, we study the convergence of the solutions and the upper semicontinuity of random attractors for the approximate equation when the perturbation parameters tend to zero. [ABSTRACT FROM AUTHOR]

In situ radioactivity measurements in a deep ocean environment are essential for marine environmental pollution monitoring and seabed geological exploration. In the past, the most widely used gamma spectrometers were based on towed instrumentation, which could only be operated underwater at a depth of less than 1500 m. In this study, a compact gamma spectrometer with small-size, light weight, and low power consumption was designed for working in a marine in situ environment. This spectrometer, with two essential parts: detector and electronics, was designed to work on different underwater platforms in the real-time control mode or autonomous operation mode. Multiple small volume avalanche photodiodes were coupled with NaI(Tl), which can significantly reduce the spectrometer volume compared with the option of the photomultiplier tube. Integrated readout electronics were employed to digitize all detector signals for miniaturization and low power consumption. The field programmable gate array (FPGA) was used to obtain the energy spectrum in real-time and an online multi-channel summation with temperature calibration algorithm was employed to improve detection efficiency. Relevant tests were also conducted in the laboratory to evaluate critical techniques and system performance. Results show that the energy resolution (full width at half maximum over the peak position) was ∼7.5% at 662 keV, verifying the online multi-channel summation with temperature calibration based on the FPGA. Moreover, the compact prototype spectrometer worked well in the power-on hydraulic test. [ABSTRACT FROM AUTHOR]

This paper is concerned with the asymptotic behavior of the solutions of the nonautonomous fractional stochastic reaction-diffusion equations on R n with continuous (but not necessarily differentiable) nonlinear drift terms, which leads to the nonuniqueness of solutions and hence a multivalued random dynamical system with the solution operators of the equation. We first show the existence and uniqueness of random attractors for such a dynamical system and then establish the upper semicontinuity of these attractors as the intensity of noise approaches zero. The measurability of the random attractors is proved by the method of weak upper semicontinuity of multivalued functions, and the pullback asymptotic compactness of the system is derived by the idea of uniform estimates on the tails of the solutions. [ABSTRACT FROM AUTHOR]

Raman spectra of InPBi alloys with bismuth amount 0.3%-2.0% were measured under hydrostatic pressure in diamond anvil cell up to ∼4 GPa at room temperature. Two bismuth related Raman modes were identified and their evolutions under pressure were studied. The linear pressure coefficients of these two modes are determined to be 1.292 and 2.169 cm-1/GPa, respectively. The different behaviors of these two modes under pressure suggest that they may have distinct origins. InP related Raman modes were also investigated including two InP related modes caused by Bi doping. [ABSTRACT FROM AUTHOR]