Boron-doped Ⅲ–Ⅴ semiconductors for Si-based optoelectronic devices

Optoelectronic devices on silicon substrates are essential not only to the optoelectronic integrated circuit but also to low-cost lasers,large-area detectors,and so forth.Although heterogeneous integration of III-V semiconductors on Si has been welldeveloped,the thermal dissipation issue and the complicated fabrication process still hinders the development of these devices.The monolithic growth of III-V materials on Si has also been demonstrated by applying complicated buffer layers or interlayers.On the other hand,the growth of lattice-matched B-doped group-III-V materials is an attractive area of research.However,due to the difficulty in growth,the development is still relatively slow.Herein,we present a comprehensive review of the recent achievements in this field.We summarize and discuss the conditions and mechanisms involved in growing B-doped group-III-V materials.The unique surface morphology,crystallinity,and optical properties of the epitaxy correlating with their growth conditions are discussed,along with their respective optoelectronic applications.Finally,we detail the obstacles and challenges to exploit the potential for such practical applications fully.

Unleashing the Power of Moiré Materials in Neuromorphic Computing

Reservoir computing has been an intriguing paradigm in the field of artificial intelligence and machine learning that draws inspiration from the complex dynamics of recurrent neural networks found in biological systems. Unlike traditional neural networks, reservoir computing separates the training of a fixed, randomly connected ‘reservoir’layer from a simpler ‘readout’ layer. This distinctive architecture allows the reservoir to process information in a highly dynamic and nonlinear manner.

Time-Domain Frequency Correction Method for Averaging Low-Field NMR Signals Acquired in Urban Laboratory Environment

Using a second-order helium-cooled superconducting quantum interference device gradiometer as the detector,ultra-low-field nuclear magnetic resonance(ULF-NMR)signals of protons are recorded in an urban environment without magnetic shielding.The homogeneity and stability of the measurement field are investigated.NMR signals of protons are studied at night and during working hours.The Larmor frequency variation caused by the fluctuation of the external magnetic field during daytime reaches around 5 Hz when performing multiple measurements for about 10 min,which seriously affects the results of averaging.In order to improve the performance of the averaged data,we suggest the use of a data processor,i.e.the so-called time-domain frequency correction(TFC).For a 50-times averaged signal spectrum,the signal-to-noise ratio is enhanced from 30 to 120 when applying TFC while preserving the NMR spectrum linewidth.The TFC is also applied successfully to the measurement data of the hetero-nuclear J-coupling in 2,2,2-trifluoroethanol.

A SQUID Bootstrap Circuit with a Large Parameter Tolerance

The voltage biased(SQUID)bootstrap circuit(SBC)was recently introduced as an effective means to reduce the preamplifier noise contribution.We analyze the tolerances of the SBC noise suppression performance to spreads in SQUID and SBC circuit parameters.It is found that the tolerance to spread mainly caused by the integrated circuit fabrication process could be extended by a one-time adjustable current feedback.A helium-cooled niobium SQUID with a loop inductance of 350 pH is employed to experimentally verify the analysis.From this work,design criteria for fully integrated SBC devices with a high yield can be derived.

Preface to the Special Issue on the Celebration of the 60th Anniversary of Dedicating to Scientific Research of Prof.Zhanguo Wang

Prof.Zhanguo Wang,a world-famous semiconductor materials physicist,was born on December 29,1938,in Zhenping County,Henan Province,China.After graduating from the Department of Physics,Nankai University in 1962,he joined the Institute of Semiconductors,Chinese Academy of Sciences,until now.Prof.Wang has made outstanding achievements in the field of semiconductor materials and material physics.He has engaged in the study of the irradiation effect of silicon solar cells used in artificial satellites and the devices/modules in nuclear transient irradiation in his early career,which significantly contributed to the realization of atomic/hydrogen bombs and artificial satellites in China.Prof.Wang joined the Department of Solid State Physics,the University of Lund,from 1980 to 1983,where he worked on deep energy level physics and photoluminescence studies of semiconductors.He and collaborators developed a new method to identify whether the two-deep levels within a bandgap are coupled,thus solving the longexisting argument for the nature of gold-related donors and acceptors in silicon and A and B deep levels in liquid phase epitaxy grown GaAs.

Generation of polarized electron beams through self-injection in the interaction of a laser with a pre-polarized plasma

Polarized electron beam production via laser wakefield acceleration in pre-polarized plasma is investigated by particlein-cell simulations.The evolution of the electron beam polarization is studied based on the Thomas±Bargmann±Michel±Telegdi equation for the transverse and longitudinal self-injection,and the depolarization process is found to be influenced by the injection schemes.In the case of transverse self-injection,as found typically in the bubble regime,the spin precession of the accelerated electrons is mainly influenced by the wakefield.However,in the case of longitudinal injection in the quasi-1D regime(for example,F.Y.Li et al.,Phys.Rev.Lett.110,135002(2013)),the direction of electron spin oscillates in the laser field.Since the electrons move around the laser axis,the net influence of the laser field is nearly zero and the contribution of the wakefield can be ignored.Finally,an ultra-short electron beam with polarization of 99%can be obtained using longitudinal self-injection.

Polarized proton beams from laser-induced plasmas

We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the particle-in-cell(PIC) simulation code VLPL(Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM, Shanghai.

Rubber–ice friction

We study the friction when a rectangular tire tread rubber block is sliding on an ice surface at different temperatures ranging from−38 to−2℃,and sliding speeds ranging from 3μm/s to 1 cm/s.At low temperatures and low sliding speeds we propose that an important contribution to the friction force is due to slip between the ice surface and ice fragments attached to the rubber surface.At temperatures above−10℃ or for high enough sliding speeds,a thin premelted water film occurs on the ice surface and the contribution to the friction from shearing the area of real contact is small.In this case the dominant contribution to the friction force comes from viscoelastic deformations of the rubber by the ice asperities.We comment on the role of waxing on the friction between skis and snow(ice particles).

Targets for high repetition rate laser facilities:needs,challenges and perspectives

A number of laser facilities coming online all over the world promise the capability of high-power laser experiments with shot repetition rates between 1 and 10 Hz. Target availability and technical issues related to the interaction environment could become a bottleneck for the exploitation of such facilities. In this paper, we report on target needs for three different classes of experiments: dynamic compression physics, electron transport and isochoric heating, and laser-driven particle and radiation sources. We also review some of the most challenging issues in target fabrication and high repetition rate operation. Finally, we discuss current target supply strategies and future perspectives to establish a sustainable target provision infrastructure for advanced laser facilities.