Quantum Supercurrent Transistors in Silicon Quantum Wells Confined by Superconductor Barriers

We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type Si (100) surface. The oscillations of the conductance in normal state and the zero-resistance supercurrent in superconductor state as a function of the top gate voltage are found to be correlated by on- and off-resonance tuning the two-dimensional levels of holes in Si-QW with the Fermi energy in the superconductor δ-barriers. The SIMS and STM studies have shown that the δ-barriers heavily doped with boron, 5 × 1021 cm–3, represent really alternating arrays of silicon empty and doped dots, with dimensions restricted to 2 nm. This concentration of boron seems to indicate that each doped dot located between empty dots contains two impurity atoms of boron. The EPR studies show that these boron pairs are the trigonal dipole centres, B+ - B–, that contain the pairs of holes, which result from the negative -U reconstruction of the shallow boron acceptors, 2B0 => B+ - B–. The electrical resistivity, magnetic susceptibility and specific heat measurements demonstrate that the high density of holes in the Si-QW (> 1011 cm–2) gives rise to the high temperature superconductor properties for the δ-barriers. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor δ-barriers. Finally, the proximity effect in the S-Si-QW-S structure is revealed by the findings of the quantization of the supercurrent and the multiple Andreev reflection (MAR) observed both across and along the Si-QW plane thereby identifying the spin transistor effect.

A highly sensitive ratiometric near-infrared nanosensor based on erbium-hyperdoped silicon quantum dots for iron(Ⅲ) detection

Ratiometric fluorescent detection of iron(Ⅲ)(Fe^(3+))offers inherent self-calibration and contactless analytic capabilities.However,realizing a dual-emission near-infrared(NIR)nanosensor with a low limit of detection(LOD)is rather challenging.In this work,we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots(Si QDs:Er),which emit NIR light at the wavelengths of 810 and 1540 nm.A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe^(3+)detection with a very low LOD(0.06μM).The effects of pH,recyclability,and the interplay between static and dynamic quenching mechanisms for Fe^(3+)detection have been systematically studied.In addition,we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.

Activation of silicon quantum dots for emission

The emission of silicon quantum dots is weak when their surface is passivated well. Oxygen or nitrogen on the surface of silicon quantum dots can break the passivation to form localized electronic states in the band gap to generate active centers where stronger emission occurs. From this point of view, we can build up radiative matter for emission. Emissions of various wavelengths can be obtained by controlling the surface bonds of silicon quantum dots. Our experimental results demonstrate that annealing is important in the treatment of the activation, and stimulated emissions at about 600 and 700 nm take place on active silicon quantum dots.

Nonlinear Doping, Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis

A series of boron- and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals （nc-Si） by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be 〈 S nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence （I3L） intensity evolution. The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.

Silicon quantum dots delivered phthalocyanine for fluorescence guided photodynamic therapy of tumor

Imaging-guided cancer therapy provides a simultaneous tumor imaging and treatment, which helps to eliminate the excessive toxicity to the healthy tissues. For this purpose, multifunctional probes capable of both imaging and curing are needed. In this work, we synthesize water-soluble silicon quantum dots（Si QDs） smaller than 5 nm. Such Si QDs are used for delivering the hydrophobic drug phthalocyanine（Pc）. The as-prepared Si/Pc nanocomposite particles show efficient transmembrane delivery into cells and feasible biocompatibility. Moreover, these composite particles emit dualchannel fluorescence signals even after cellular internalization and demonstrate robust photostability in the Si channel.More interestingly, the Si/Pc composite particles show efficient photodynamic therapy effects against tumors both in vitro and in vivo.

硅基InGaN/GaN多量子阱微盘器件的发光、探测和数据传输

光源和探测器的集成可有效促进轻量化和小型化光电系统的发展,InGaN/GaN多量子阱器件中发光与探测共存现象为收发一体芯片的设计提供了可能。本文采用标准半导体工艺制备了硅片上集成的圆盘形InGaN/GaN多量子阱阵列器件,并对其发光、探测以及基本通信特性进行了研究。微盘型器件中的共振模式有助于提升其探测特性,同时各向同性的辐射特性有助于器件作为光源时与探测器在空间上的耦合。作为光源,该器件的开启电压为2.5 V,中心波长455 nm,-3 dB带宽为5.4 MHz。作为探测器,该器件对紫外到蓝光波段的光有响应,探测性能随波长增加而减弱,截止波长450 nm。在365 nm光源激发下,该器件具有最高开关比7.2×10^(4),下降沿时间为0.41 ms。同时,基于单个微盘器件,本文构建并演示了半双工通信系统,在不同频段实现数据传输。这项研究对于电驱动光源制备以及收发一体的光通信具有重要意义。

Silicon quantum dots-based fluorescent sensor for the detection of cobalt with high sensitivity and selectivity

Fluorescent silicon quantum dots(Si QDs)were hydrothermally synthesized from a mixture of 3(2-aminoethylamino)propyl(dimethoxymethylsilane)(AEAPDMMS)and poly(vinylpyrrolidine)(PVP).The resulting Si QDs exhibited good water solubility and high stability.Under the optimized conditions,the probe revealed an excellent linear fluorescence quenching effect on Co2+ranging from 1μmol/L to 120μmol/L with a limit of detection of 0.37μmol/L(based on 3 s/k).The quenching mechanism was studied,showing that static quenching(SQE)causes the main effect.Furthermore,the test paper based on Si QDs was prepared,which is cost-effective,high sensitivity,good selectivity,easy to use and show excellent anti-interference capability.This method was applied to analyze the content of Co2+in environmental water samples with satisfying results.

Bifunctional Silicon Quantum Dots for Antibacterial Application and Highly Sensitive Detection of Tetracycline

Silicon quantum dots(SiQDs)with high water-soluble and favorable photostability were prepared by a one-step hydrothermal method.The average diameter of SiQDs was 2.02 nm characterized by transmission electron microscope.It was to be noted that the as-prepared SiQDs showed eff ective antibacterial activity,which was attributed to electrostatic interaction and the generation of reactive oxygen species.The minimum inhibitory concentration of SiQDs against Escherichia coli and Staphylococcus aureus was 0.45 mg/mL and 0.38 mg/mL,respectively.Besides,based on the static quenching eff ect-induced fluorescence quenching mechanism,the SiQDs exhibited high sensitivity and selectivity for detecting tetracyclines(TC).A good linear relationship was obtained between the fluorescence intensity of SiQDs and the concentration of tetracycline(TC)in the range of 0–0.08μmol/L(R^(2)=0.9993)with a detection limit of 0.0176μmol/L.Furthermore,the TC content in the honey samples was determined using the SiQDs.All the results suggest that the as-prepared SiQDs can be a potential fluorescent probe for application in antibacterial and analysis.

SiGe电光调制器研究进展

光子调制器是光纤通信系统中的核心器件,主要对光信号进行调制,实现信号从电域到光域的转换。随着硅基半导体工艺的发展,硅基光子调制器逐渐成为了主流硅光子器件,基于硅工艺技术的GHz带宽调制器的实现也为硅光子学的发展奠定了基础。作为一种用于短距离光互连的高性能光调制器,SiGe光吸收调制器受到了较多关注。文中讨论了高性能SiGe电光调制器的发展现状,对国内外硅基光子调制器的研究进展进行分析,讨论了PIN、PN结等电学调制结构,为研发高速率、低损耗的光子调制器提供了思路。

EDESR and ODMR of Impurity Centers in Nanostructures Inserted in Silicon Microcavities

We present the first findings of the new electrically- and optically-detected magnetic resonance technique [ED electron spin resonance (EDESR) and (ODMR)] which reveal single point defects in the ultra-narrow silicon quantum wells (Si-QW) confined by the superconductor δ-barriers. This technique allows the ESR identification without the application of the external cavity as well as a high frequency source and recorder, with measuring the only magnetoresistance (EDESR) and transmission (ODMR) spectra within frameworks of the excitonic normal-mode coupling (NMC) caused by the microcavities embedded in the Si-QW plane. The new resonant positive magnetoresistance data are interpreted here in terms of the interference transition in the diffusive transport of free holes respectively between the weak antilocalization regime in the region far from the ESR of a paramagnetic point defect located inside or near the conductive channel and the weak localization regime in the nearest region of the ESR of that defect.

用于单片集成的硅基外延Ⅲ-Ⅴ族量子阱和量子点激光器研究

硅基光电子技术以光电子与微电子的深度融合为特征,是后摩尔时代的核心技术。硅基光电子芯片可以利用成熟的微电子平台实现量产,具有功耗低、集成密度大、传输速率快、可靠性高等优点,广泛应用于数据中心、通信系统等领域。除硅基激光器外,硅基光探测器、硅基光调制器等硅基光电子器件技术已经基本成熟,但作为最有希望实现低成本、大尺寸单片集成的硅基外延激光器仍然面临着诸多挑战。在此背景下,本文从直接外延无偏角Ⅲ-Ⅴ/Si(001)衬底、无偏角硅基激光器材料、外延技术,以及单片集成等方面探讨了近些年国内外硅基光源的研究进展,重点介绍了本研究组在硅基外延Ⅲ-Ⅴ族量子阱和量子点激光器方面的研究进展,包括无反相畴GaAs/Si(001)衬底的制备、硅基InGaAs/AlGaAs量子阱激光器材料外延、硅基InAs/GaAs量子点激光器材料外延和新型并联方式共面电极硅基激光器芯片制作等。

Preparation and Evaluation of Silicon Quantum Dots-Bonded Silica Stationary Phase for Reversed-Phase Chromatography

In this paper,silicon quantum dots(SiQDs)with green fluorescence are synthesized by solvothermal reaction of 3-(2,3-epoxypropoxy)propyltrimethoxysilane(GPTMS)and ethylenediaminetetraacetic acid(EDTA),and then SiQDs are bonded to the surface of silica to obtain a new nano-on-micro stationary phase(SiO_(2)-SiQDs)for reversed-phase chromatography.The successful preparation of SiO_(2)-SiQDs stationary phase is demonstrated by a variety of characterizations,such as transmission electron microscopy,laser confocal microscopy,elemental analysis and Fourier infrared spectroscopy.In addition,the chromatographic performance of the prepared stationary phase is evaluated and it shows good separation performance for non-polar substances such as alkylbenzene,aniline and polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography.It is also verified that the stationary phase has good methyl selectivity and shape selectivity.More interestingly,the separation of prednisolone and hydrocortisone isomers can also be achieved at a low ratio of organic solvents,indicating that this new stationary phase has a good application prospect in isomer separation.

硅基低维红外探测薄膜材料的研究概况

Si基探测器与硅读出电路的单片集成不仅使光电芯片在性能上得到重要改善,还可极大地降低成本。在对量子阱、量子点原理描述的基础上,综述了它们应用于薄膜红外探测材料的研究进展,提出了近期工作的重点。

红外区熔再结晶SOI GE_XSi_(1-X)合金沟道P-MOSFET的研究

在红外区熔再结晶SOI材料上用MBE的方法形成Si／GexSi1－x／Si量子阱结构．在此基础上，采用常规的P－MOS工艺制造出了SOIGexSi1-x合金沟道P－MOSFET．为避免GexSi1-x合金材料发生蜕化，MBE以后除快速热退火（RTA）以外的所有工艺温度都不超过800℃．直流特性的测量结果表明，与普通Si沟道器件相比，GexSi1-x合金沟道器件的沟道载流子迁移率有所提高．而且，这种器件在性能的进一步提高方面存在着相当大的潜力．

Ultrafast optical spectroscopy of surface-modified silicon quantum dots: unraveling the underlying mechanism of the ultrabright and color-tunable photoluminescence

In this work,the fundamental mechanism of ultrabright fluorescence from surface-modified colloidal silicon quantum dots is investigated in depth using ultrafast spectroscopy.The underlying energy band structure corresponding to such highly efficient direct bandgap-like emissions in our surface-modified silicon quantum dots is unraveled by analyzing the transient optical spectrum,which demonstrates the significant effect of surface molecular engineering.It is observed that special surface modification,which creates novel surface states,is responsible for the different emission wavelengths and the significant improvement in the photoluminescence quantum yields.Following this essential understanding,surface-modified silicon quantum dots with deep blue to orange emission are successfully prepared without changing their sizes.

Quantum dot lasers for silicon photonics [Invited]

We review recent advances in the field of quantum dot lasers on silicon. A summary of device performance,reliability, and comparison with similar quantum well lasers grown on silicon will be presented. We consider the possibility of scalable, low size, weight, and power nanolasers grown on silicon enabled by quantum dot active regions for future short-reach silicon photonics interconnects.

锗硅量子阱异质界面附近缺陷研究

用深能级瞬态谱（ＤＬＴＳ）研究了量子阱样品价中载流子的热发射和异质界面附近的深能级缺陷，得到Ｓｉ０．６７Ｇｅ０．３３／Ｓｉ单量子样品的能带偏移为０．２４ｅＶ．量子阱异质界面附近高浓度的深能级缺陷在样品的ＤＬＴＳ谱上形成一少于峰，该信号只有当测量的脉冲宽度足够大时才能检测到．对比不；司组分相同结构的多量子阱样品发现，组分大时异质界面的深能级缺陷浓度大，因此它可能是失配应变或位错引起的．相应的光致发光谱（ＰＬ）测试结果表明该深能级缺陷还会导致ＰＬ谱中合金层的带边激子峰的湮灭．

Plasmonic silicon quantum dots extend photodetection into mid-infrared range

Nowadays the development of Internet of Things(IoT)and defense technologies imperatively needs high-performance photodetectors that can work in a broadband wavelength range,in particular,covering the mid-infrared(MIR)region[1].This generates great interest in the incorporation of a series of novel optoelectronic materials and structures into the photodetectors.Graphene and colloidal quantum dots(QDs)are key players among novel materials used to fabricate high-performance photodetectors[2–4].By taking advantage of the high mobility of

Generation and dynamic manipulation of frequency degenerate polarization entangled Bell states by a silicon quantum photonic circuit

A silicon quantum photonic circuit was proposed and realized for the generation and the dynamic manipulation of telecom-band frequency-degenerate polarization entangled Bell states.Frequency degenerate biphoton states were generated in four silicon waveguides by spontaneous four wave mixing.They were transformed to polar-ization entangled Bell states through on-chip quantum interference and quantum superposition,and then coupled to optical fibers.The property of polarization entanglement in generated photon pairs was demonstrated by two-photon interference under two non-orthogonal polarization bases.The output state could be dynamically switched between two Bell states,which was demonstrated by the simplified Bell state measurement.The experiment results indicated that the manipulation speed supported a modulation rate of several tens kHz,showing its potential on applications of quantum communication and quantum information processing requiring Bell state encoding and dynamic control.

Supercell Approach in Tight-Binding Calculation of Si and Ge Nanowire Bandstructures

Energy bandstructures of [100] oriented Si and Ge quantum nanowires with various cross-sections are calculated by using the sp^3d^5s^＊ tight-binding model with a supercell approach. Results are compared with those obtained by the first principles method （i.e., density functional theory, or DFT）. The differences in the bandstructure between silicon and germanium nanowires are analysed and it is shown that germanium keeps indirect-bandgap and the silicon nanowire along the [100] direction becomes direct-bandgap when the wire diameter shrinks. It is shown in comparison with the available experimental data that the tight-binding method is adequate in predicting the bandstructure parameters relevant to the carrier transport in mesoscopic nanowire devices and is far superior to the DFT method in terms of computational cost.