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In this paper, we report a new method to generate tunable high-repetition-rate temporal cavity solitons (TCSs) in a nonlinear fiber cavity, which is driven by dual Brillouin laser pulses. This method is more feasible than generating solitons via a continuous optical-driven nonlinear cavity because of the enhanced four-wave mixing process triggered by the high peak intensity Brillouin laser pulses. The generated TCSs lock to the beating signal arriving from dual Brillouin pulses, which allows the repetition rate of the solitons to be directly tuned all- optically. The TCSs can be continuously tuned over a repetition rate range of 140∼242 GHz by controlling the external dual-wavelength spacing, and the pulse duration can be accordingly adjusted from 0.9 ps to 513 fs. Such TCSs with tunable high-repetition-rate can provide a practical solution for the low-noise controllable millimeter-wave and terahertz sources. [ABSTRACT FROM AUTHOR]

This work demonstrates vertical $\boldsymbol {\beta } $ -Ga2O3 Schottky barrier diodes (SBDs) breaking through the power figure of merit of 1 GW/cm2 without edge termination. The unreliable surface on the top of $\sim {1.2}\times {10} ^{{16}}$ cm−3 drift region, which naturally formed in air, was removed by inductively coupled plasma etching. The repaired surface was exposed to ambient air for less than 10 minutes during the entire preparation process. Compared with the excessive air exposure samples, the leakage current was well suppressed for the Ni/ $\boldsymbol {\beta } $ -Ga2O3 SBDs fabricated on a clean surface. Moreover, the blocking voltage reaches a maximum value of 1720 V, and the forward/reverse characteristics of the diodes on the same wafer show good uniformity. These results pave the way for further improving the performance of $\boldsymbol {\beta }$ -Ga2O3 devices and verify the potential of $\boldsymbol {\beta }$ -Ga2O3 SBDs for power applications. [ABSTRACT FROM AUTHOR]

This work reports a $\beta $ -Ga2O3 double-barrier Schottky barrier diode (DBSBD) with both low turn-on voltage and low reverse leakage current by using Ni and PtOx as the anode electrode. The barrier height of PtOx-based diode can be effectively modulated from 1.26 to 1.62 eV by adjusting oxygen pressure during sputtering processes. Combining the maximum work function of PtOx electrode with the optimization of the electrode ratio of Ni and PtOx, the DBSBD with an electrode diameter ratio of $\text{D}_{\text {Ni}} /\text{D}_{\text {PtOx}}= {75}/{150} \mu \text{m}$ not only exhibits a high forward current of 470.9 A/cm2 (at 3.5 V), a low on-resistance of 4.1 $\text{m}\Omega ~\cdot $ cm2 and a low turn-on voltage of 1.13 V, but also possesses a relatively low reverse leakage current of ${1.2}\times {10}^{-{7}}$ A/cm2 (at −100 V), which is more than one order of magnitude lower than that of the Ni-SBD. Silvaco TCAD simulation reveals that such optimization can be attributed to the suppression of edge leakage current due to the double-barrier contact. Therefore, the strategy of double-barrier design can balance the forward and reverse characteristics in SBD, providing a new device structure for advanced power electronics. [ABSTRACT FROM AUTHOR]

In this letter, trench-gate metal–oxide–semiconductor field-effect transistors on (010) $\beta $ -Ga2O3 epitaxial layer are fabricated. Enhancement mode is achieved by the gate-recess process, through thoroughly depleting the $\beta $ -Ga2O3 channel to get a positive threshold voltage. For the first time, by using a dynamic parameter test system, the Ga2O3 MOSFET with 2- $\mu \text{m}$ gate length is characterized to present short switching time, including turn-on time ($\textit {t}_{ \mathrm{\scriptscriptstyle ON}}$) of 28.6 ns and turn-off time ($\textit {t}_{ \mathrm{\scriptscriptstyle OFF}}$) of 94.0 ns. In addition, OFF-state interelectrode parasitic capacitances, including input capacitance ($\textit {C}_{\text {iss}}$) of 37 pF/mm, output capacitance ($\textit {C}_{\text {oss}}$) of 42 pF/mm, and reverse transfer capacitance ($\textit {C}_{\text {rss}}$) of 14 pF/mm are also obtained, which can account for the high switching speed. The static and dynamic switching properties of the trench-gate device show the potential of $\beta $ -Ga2O3 MOSFET for the high-speed switching applications. [ABSTRACT FROM AUTHOR]

In this paper, we study user selection (US) strategies for a multiple-input–multiple-output (MIMO) cognitive radio (CR) downlink network, where the r-antenna underlay CR secondary users (SUs) coexist with a primary user (PU), and all terminals are equipped with multiple antennas. Two main scenarios are considered: 1) The t-antenna cognitive base station (CBS) has perfect or partial channel state information at the transmitter (CSIT) from the CBS to the PU receiver (RX), and 2) the CBS has absolutely no PU CSIT. For these scenarios, we propose and evaluate multiple SU selection schemes that are applicable to both best-effort PU interference mitigation and hard interference temperature (IT) constraints. The computational complexity of the proposed schemes can be significantly smaller than that of an exhaustive search with negligible performance degradation. For the selection of C SUs out of K, whereas an exhaustive search is on the order of \mathcal{O}(\binom{K}{C}C^4r^3). When t$ and r$ are of the same order, the computational complexity of the proposed scheme can be \binom{K}{C}C^4/K times smaller. Mathematical complexity analysis and numerical simulations are provided to show the advantage of our schemes. [ABSTRACT FROM PUBLISHER]