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To improve the threshold voltage and gate reliability of conventional enhancement-mode p-GaN-gated AlGaN/GaN high electron mobility transistors while maintaining a low on-resistance, an improved design solution for p-GaN HEMTs with P-I-N junction gate (PIN-HEMTs) has been proposed. Simulation results show that energy band modulation is achieved by adjusting the doping concentration and thickness of each layer of the PIN junction, and high-performance p-GaN gate HEMTs with adjustable threshold voltages ranging from 0.56 V to 4.75 V and gate breakdown voltages ranging from 19.8 V to 30.3 V would be prepared. The PIN-HEMT has a quasi-self-alignment property, which means that good gate control is independent of gate metal alignment. This not only improves the production efficiency but also solves the problems of weak gate control and electric field aggregation at the gate edge caused by the gate misalignment in conventional p-GaN gate HEMTs, thus realizing lower on-resistance and higher gate breakdown voltage, which demonstrates this proposed structure has excellent potentials for realizing effective and reliable high-power transistors. [ABSTRACT FROM AUTHOR]

In this work, a high performance GaN-on-Si quasi vertical PiN diode was demonstrated by the combination of a beveled sidewall and self-aligned fluorine plasma treatment. The didoes achieved a remarkable breakdown voltage ($\text{V}_{\text {BR}}{)}$ of 930 V and an ultra-low reverse leakage current. Meanwhile the didoes showed a low specific on-resistance ($\text{R}_{ \mathrm{\scriptscriptstyle ON},\textit {sp}}$) of 0.43 $\text{m}\Omega \cdot $ cm2, a high on/off current ratio ($\text{I}_{ \mathrm{\scriptscriptstyle ON}}/\text{I}_{ \mathrm{\scriptscriptstyle OFF}}$) of $10^{{11}}$ , and an excellent Baliga’s figure of merit (BFOM) of 2.01 GW/cm2. The measurement results of X-ray spectroscopy (XPS) and Kelvin Probe Force Microscopy (KPFM) proved the presence of F ions and the decrease of surface potential, which reduced the electric field peak and suppressed the leakage current. These results show a great potential of GaN on Si PiN diode for power applications. [ABSTRACT FROM AUTHOR]

This article introduces and explores the current frontier four-legged (quadruped) and six-legged (hexapod) crawling micro-robots. The performances of various crawling micro-robots are compared, and their driving modes are analyzed. Moreover, the research status of crawling micro-robots is summarized, and the future application prospects and development directions of these robots are put forward. [ABSTRACT FROM AUTHOR]

To realize the complementary circuit on the GaN-on-Si platform, an investigation of p-channel heterostructure field-effect transistors (p-HFETs) is necessary. In this study, an analytical model for the estimation of the threshold voltage (${V}_{\text {TH}}$) for GaN-based p-HFETs was developed. In this model, the impact of polarization charges at different interfaces, the influence of interface charges at oxide/GaN interface, as well as the out-diffusion effect of Mg dopant in the p-GaN layer were all taken into consideration for systematic exploration. Herein, GaN-based p-HFETs were fabricated to verify the relationship between the ${V}_{\text {TH}}$ and the thickness of the GaN channel layer by using the proposed model. The ${V}_{\text {TH}}$ model was further confirmed through TCAD simulations. The influences of the thickness of oxide layer, Mg doping concentration in p-GaN layer, and the Al mole fraction of AlxGa $_{{1}-{x}}\text{N}$ layer on ${V}_{\text {TH}}$ were also discussed in detail. The model serves as more accurate guidance for the optimization of such p-HFETs design and complementary circuits. [ABSTRACT FROM AUTHOR]

The gate and drain bias dependence of hot electron-induced degradation in GaN-based metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) was investigated in this work. Devices exhibit an abnormal increase in peak transconductance (${G}_{m}$ ,max) during hot carrier stress (HCS) and a partially quick recovery of that after removing the electrical stress. A physical model is proposed to explain the abnormal electrical characteristics caused by HCS. By using density functional theory (DFT), we calculated the energy for electrons to dehydrogenate preexisting [NGaH3]−1 complexes in GaN layer during stress. The dehydrogenation of defects affects the Gm,max of devices. Meanwhile, the neutralization of donor traps in AlGaN barrier layer also plays a significant role in the increase of Gm,max and the detrapping effect of electrons from these traps after removing the electrical stress accounts for the partially quick recovery of ${G}_{m, \text{max}}$. [ABSTRACT FROM AUTHOR]

Working memory (WM) is a fundamental cognitive ability to support complex thought, but it is limited in capacity. WM training has shown the potential benefit for those in need of a higher WM ability. Many studies have shown the potential of transcranial direct current stimulation (tDCS) to transiently enhance WM performance by delivering a low current to the brain cortex of interest, via electrodes on the scalp. tDCS has also been revealed as a promising intervention to augment WM training in a few studies. However, those few tDCS-paired WM training studies, focused more on the effect of tDCS on WM enhancement and its transferability after training and paid less attention to the variation of cognitive performance during the training procedure. The current study attempted to explore the effect of tDCS on the variation of performance, during WM training, in healthy young adults. All the participants received WM training with the load-adaptive verbal N-back task, for 5 days. During the training procedure, active/sham anodal high-definition tDCS (HD-tDCS) was used to stimulate the left dorsolateral prefrontal cortex (DLPFC). To examine the training effect, pre- and post-tests were performed, respectively, 1 day before and after the training sessions. At the beginning of each training session, stable-load WM tasks were performed, to examine the performance variation during training. Compared to the sham stimulation, higher learning rates of performance metrics during the training procedure were found when WM training was combined with active anodal HD-tDCS. The performance improvements (post–pre) of the active group, were also found to be higher than those of the sham group and were transferred to a similar untrained WM task. Further analysis revealed a negative relationship between the training improvements and the baseline performance. These findings show the potential that tDCS may be leveraged as an intervention to facilitate WM training, for those in need of a higher WM ability. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT) film has great potential in the application as a cold cathode in vacuum power electron devices. Pulse field emission of CNT film is investigated to achieve large current and current density. A maximum current of 16 mA is obtained from a 0.02-cm^2 CNT film with a current density of 800 mA/cm^2. The pulsewidth and area of CNT film have strong effects on field emission characteristics of CNT film, such as total current, current density, and current stability. The reason for this is discussed in detail. The results are useful for the design of the large current and current density CNT cold cathodes. [ABSTRACT FROM AUTHOR]