Design, Fabrication, and Modeling of CMOS-Compatible Double Photodiode

A double photodiode(PD) constructed by p^+/N-well junction and N-well/p-sub junction was designed and fabricated in a UMC 0.18-lm CMOS process. Based on the device structure and mechanism of double PD, a novel small-signal equivalent circuit model considering the carrier transit effect and the parasitic RC time constant was presented. By this model with complete electronic components, the double PD can be incorporated in a commercial circuit simulator. The component values were extracted by fitting the measured S-parameters using simulated annealing algorithm, and a good agreement between the measurement and the simulation results was achieved.

Controlling spins in silicon quantum dots

Spins in silicon(Si)quantum dots(QDs),as a new type of solid state qubits,is expected to be a competitive contender in the long run of scalable quantum computation[1].Quantum computation is believed to be the next-generation computing technology to solve the problems that no classical computer can feasibly tackle.In the last decade.

Acupuncture preconditioning protects hippocampal neurons from transient ischemia/reperfusion injury

The present study established a model of brain ischemia in aged rats using four-vessel occlusion.We observed hippocampal CA1 neuronal apoptosis and apoptosis-mediated protease caspase-3 expression following preconditioning of electroacupuncture at Baihui（GV 20）.Our results showed that the number of hippocampal CA1 normal neurons was decreased,and degenerated neurons were increased 12 hours to 3 days following cerebral ischemia/reperfusion.The number of hippocampal CA1 apoptotic neurons and caspase-3-positive neurons in rats with cerebral ischemia/reperfusion injury was significantly decreased following acupuncture preconditioning.Acupuncture preconditioning protects aged rats against ischemia/reperfusion injury by regulating caspase-3 protein expression.

Impact of Al_(x)Ga_(1-x)N barrier thickness and Al composition on electrical properties of ferroelectric HfZrO/Al_(2)O_(3)/AlGaN/GaN MFSHEMTs

Ferroelectric(FE)HfZrO/Al_(2)O_(3) gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mo-bility transistors(MFSHEMTs)with varying Al_(x)Ga_(1-x)N barrier thickness and Al composition are investigated and com-pared by TCAD simulation with non-FE HfO_(2)/Al_(2)O_(3) gate stack metal-insulator-semiconductor heterostructure high-electron mobility transistors(MISHEMTs).Results show that the decrease of the two-dimensional electron gas(2DEG)density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHEMTs due to the enhanced FE polarization switching efficiency.The electrical characteristics of MFSHEMTs,including transcon-ductance,subthreshold swing,and on-state current,effectively improve with decreasing AlGaN thickness in MFSHEMTs.High Al composition in AlGaN barrier layers that are under 3-nm thickness plays a great role in enhancing the 2DEG den-sity and FE polarization in MFSHEMTs,improving the transconductance and the on-state current.The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs,affording favorable conditions for further enhancing the device.

甘蓝型油菜EXA1的克隆及其对植物抗病的调控作用

拟南芥(Arabidopsis thaliana)EXA1缺失会导致exa1-2突变体植株PR基因表达上调,对病原菌的抗性提高。该研究通过克隆甘蓝型油菜(Brassica napus)中的BnaEXA1,并将其在拟南芥exa1-2突变体中异源超表达,发现BnaEXA1超表达不仅可恢复突变体的表型,而且显著降低突变体中PR1和PR2基因的表达量,导致其对核盘菌(Sclerotinia sclerotiorum)和卵菌H.a.Noco2易感,表明BnaEXA1调控植物的基础抗性。

A reconfigurable terahertz polarization converter based on metal–graphene hybrid metasurface

A metal-graphene hybrid metasurface polarization converter is designed in this Letter.The unit cell of the hybrid metasurface is composed of a butterfly-shaped structure whose branches are connected by multi-layer graphene sheets.The proposed device can be reconfigured from linear-to-circular polarization to cross-polarization by changing the Fermi energy of graphene.The simulation results show that for three-layer graphene,the device acts as a linear-to-circular polarization converter when EF=0 eV and switches to a cross-polarization converter when EF=0.5 eV.Compared with single-layer graphene,the device with three-layer graphene can maintain the cross-polarization conversion performance under low Fermi energy.Furthermore,two equivalent circuits in the x and y directions are developed to understand the working mechanism of the device.

Radio-frequency measurement in semiconductor quantum computation

Semiconductor quantum dots have attracted wide interest for the potential realization of quantum computation.To realize efficient quantum computation,fast manipulation and the corresponding readout are necessary.In the past few decades,considerable progress of quantum manipulation has been achieved experimentally.To meet the requirements of high-speed readout,radio-frequency(RF)measurement has been developed in recent years,such as RF-QPC(radio-frequency quantum point contact)and RF-DGS(radio-frequency dispersive gate sensor).Here we specifically demonstrate the principle of the radio-frequency refiectometry,then review the development and applications of RF measurement,which provides a feasible way to achieve high-bandwidth readout in quantum coherent control and also enriches the methods to study these artificial mesoscopic quantum systems.Finally,we prospect the future usage of radio-frequency refiectometry in scaling-up of the quantum computing models.

基于微波光子长程耦合的半导体量子比特相关谱研究

本文利用高阻抗微波谐振腔实现了两个半导体量子比特间的长程耦合,并在此基础上进一步开发了一种新型谱学方法,快速、直观地表征了量子比特之间的耦合关系.运用该谱学方法,实验上测量得到一系列随隧穿耦合速率变化的独特、高辨识度的图谱,且通过这些图谱可以快速定性地判断两个比特的耦合区间,并与利用Tavis-Cummings模型得到的模拟结果高度一致.本文从一个新的角度(参数空间)对腔电动力学杂化系统进行表征,提供了一种在多比特情况下也适用的新型谱学表征方法,有效提高了表征多比特杂化系统、调制比特参数的效率,为研究以光子为耦合媒介的多比特系统相互作用提供了新的研究思路.

Enhanced readout of spin states in double quantum dot

We investigate a spin-to-charge conversion mechanism which maps the spin singlet and triplet states to two charge states differing by one electron mediated by an intermediate metastable charge state. This mechanism allows us to observe fringes in the spin-unblocked region beyond the triplet transition line in the measurement of the exchange oscillations between singlet and triplet states in a four-electron double quantum dot. Moreover, these fringes are amplified and p-phase shifted, compared with those in the spin blockade region. Unlike the signal enhancement mechanism reported before which produces similar effects, this mechanism only requires one dot coupling to the lead, which is a commonly encountered case especially in imperfect devices. Besides, the crucial tunnel rate asymmetry is provided by the dependence on spin state, not by the asymmetric couplings to the leads. We also design a scheme to control the amplification process, which enables us to extract the relevant time parameters. This mechanism will have potential applications in future investigations of spin qubits.

Kerr effect in ultra-compact hybrid plasmonic metal-insulator-metal nano-focusing structure

Nano-focusing structures based on hybrid plasmonic waveguides are likely to play a key role in strong nonlinear optical devices.Although the insertion loss is considerable,a significant nonlinear phase shift may be achieved by decreasing the nano-focusing device footprint and careful parameter optimization.Here,we study the Kerr effect in hybrid plasmonic waveguides by analyzing the mode effective area,energy velocity,and insertion loss.Particularly,by utilizing plasmonics to manipulate the effective index and mode similarity,the TM mode is reflected and absorbed,while the TE mode passes through with relatively low propagation loss.By providing a deep understanding of hybrid plasmonic waveguides for nonlinear applications,we indicate pathways for their future optimization.

Band-gap tunable(Ga_(x)In_(1−x))_(2)O_(3)layer grown by magnetron sputtering

Multicomponent oxide(Ga_(x)In_(1−x))_(2)O_(3)films are prepared on(0001)sapphire substrates to realize a tunable band-gap by magnetron sputtering technology followed by thermal annealing.The optical properties and band structure evolution over the whole range of compositions in ternary compounds(Ga_(x)In_(1−x))_(2)O_(3)are investigated in detail.The X-ray diffraction spectra clearly indicate that(Ga_(x)In_(1−x))_(2)O_(3)films with Ga content varying from 0.11 to 0.55 have both cubic and monoclinic structures,and that for films with Ga content higher than 0.74,only the monoclinic structure appears.The transmittance of all films is greater than 86%in the visible range with sharp absorption edges and clear fringes.In addition,a blue shift of ultraviolet absorption edges from 380 to 250 nm is noted with increasing Ga content,indicating increasing band-gap energy from 3.61 to 4.64 eV.The experimental results lay a foundation for the application of transparent conductive compound(Ga_(x)In_(1−x))_(2)O_(3)thin films in photoelectric and photovoltaic industry,especially in display,light-emitting diode,and solar cell applications.