Application of nano-patterned InGaN fabricated by selfassembled Ni nano-masks in green InGaN/GaN multiple quantum wells

The nano-patterned InGaN film was used in green InGaN/GaN multiple quantum wells(MQWs)structure,to relieve the unpleasantly existing mismatch between high indium content InGaN and GaN,as well as to enhance the light output.The different self-assembled nano-masks were formed on InGaN by annealing thin Ni layers of different thicknesses.Whereafter,the InGaN films were etched into nano-patterned films.Compared with the green MQWs structure grown on untreated InGaN film,which on nano-patterned InGaN had better luminous performance.Among them the MQWs performed best when 3 nm thick Ni film was used as mask,because that optimally balanced the effects of nano-patterned InGaN on the crystal quality and the light output.

Room-temperature ferromagnetism and piezoelectricity in metalfree 2D semiconductor crystalline carbon nitride

Two-dimensional(2D)materials that combine ferromagnetic,semiconductor,and piezoelectric properties hold significant potential for both fundamental research and spin electronic devices.However,the majority of reported 2D ferromagnetic-semiconductor-piezoelectric materials rely on d-electron systems,which limits their practical applications due to a Curie temperature lower than room temperature(RT).Here,we report a high-crystallinity carbon nitride(CCN)material based on sp-electrons using a chemical vapor deposition strategy.CCN exhibits a band gap of 1.8 eV and has been confirmed to possess substantial in-plane and out-of-plane piezoelectricity.Moreover,we acquired clear evidences of ferromagnetic behavior at room temperature.Extensive structural characterizations combined with theoretical calculations reveal that incorporating structural oxygen into the highly ordered heptazine structure causes partial substitution of nitrogen sites,which is primarily responsible for generating room-temperature ferromagnetism and piezoelectricity.As a result,the strain in wrinkles can effectively modulate the domain behavior and piezoelectric potential at room temperature.The addition of RT ferromagnetic-semiconductor-piezoelectric material based on sp-electrons to the family of two-dimensional materials opens up numerous possibilities for novel applications in fundamental research and spin electronic devices.

Two-dimensional electron gas characteristics of InP-based high electron mobility transistor terahertz detector

The samples of InxGa（1-x）As/In（0.52）Al（0.48）As two-dimensional electron gas（2DEG）are grown by molecular beam epitaxy（MBE）.In the sample preparation process,the In content and spacer layer thickness are changed and two kinds of methods,i.e.,contrast body doping andδ-doping are used.The samples are analyzed by the Hall measurements at 300 Kand 77 K.The InxGa1-xAs/In0.52Al0.48As 2DEG channel structures with mobilities as high as 10289 cm^2/V·s（300 K）and42040 cm^2/V·s（77 K）are obtained,and the values of carrier concentration（Nc）are 3.465×10^12/cm^2 and 2.502×10^12/cm^2,respectively.The THz response rates of In P-based high electron mobility transistor（HEMT）structures with different gate lengths at 300 K and 77 K temperatures are calculated based on the shallow water wave instability theory.The results provide a reference for the research and preparation of In P-based HEMT THz detectors.

High-power microwaves response characteristics of silicon and GaAs solar cells

The high-power microwave(HPM)effect heats solar cells,which is an important component of a satellite.This creates a serious reliability problem and affects the normal operation of a satellite.In this paper,the different HPM response characteristics of two kinds of solar cells are comparatively researched by simulation.The results show that there are similarities and differences in hot spot distribution and damage mechanisms between both kinds of solar cell,which are related to the amplitude of HPM.In addition,the duty cycle of repetition frequency contributes more to the temperature accumulation of the solar cells than the carrier frequency.These results will help future research of damage assessment technology,reliability enhancement and the selection of materials for solar cells.

Ge/Si heterojunction L-shape tunnel field-effect transistors with hetero-gate-dielectric

A Ge/Si heterojunction L-shaped tunnel field-effect transistor combined with hetero-gate-dielectric （GHL-TFET） is proposed and investigated by TCAD simulation. Current-voltage characteristics, energy-band diagrams, and the distri- bution of the band-to-band tunneling （BTBT） generation rate of GHL-TFET are analyzed. In addition, the effect of the vertical channel width on the ON-current is studied and the thickness of the gate dielectric is optimized for better suppression of ambipolar current. Moreover, analog/RF figure-of-merits of GHL-TFET are also investigated in terms of the cut-off frequency and gain bandwidth production. Simulation results indicate that the ON-current of GHL-TFET is increased by about three orders of magnitude compared with that of the conventional L-shaped TFET. Besides, the introduction of the hetero-gate-dielectric not only suppresses the ambipolar current effectively but also improves the analog/RF performance drastically. It is demonstrated that the maximum cut-off frequency of GHL-TFET is about 160 GHz, which is 20 times higher than that of the conventional L-shaped TFET.

Germanium PMOSFETs with Low-Temperature Si2H6 Passivation Featuring High Hole Mobility and Superior Negative Bias Temperature Instability

We investigate negative bias temperature instability （NBTI） on high performance Ge p-channel metal-oxide- semiconductor field-effect transistors （pMOSFETs） with low-temperature Si2H6 passivation. The Ge pMOSFETs exhibit an effective hole mobility of 311 cm2/V.s at an inversion charge density of 2.5 × 1012 cm^-2. NBTI characterization is performed to investigate the linear transconductance （GM,lin） degradation and threshold voltage shift （△VTH） under NBT stress. Ge pMOSFETs with a lOyr lifetime at an operating voltage of -0.72 V are demonstrated. The impact of the Si2H6 passivation temperature is studied. As the passivation temperature increases from 350℃ to 550℃, the degradation of NBTI characteristics, e.g., GM,lin loss, △VTH and an operating voltage for a lifetime of lOyr, is observed.

Simulating tactile and visual multisensory behaviour in humans based on an MoS_(2) field effect transistor

A visual and tactile multisensory integrated system is essential for human walking due to the demand for real-time interactions between perception and action.Here,a piezoresistor and MoS_(2)field effect transistor are combined to construct an artificial integration nervous system to simulate perception and synaptic plasticity.The key characteristics of synaptic plasticity are successfully demonstrated by individual pressure signals,individual optical signals,the synergy of optical and pressure signals,which are based on the electron trapping–detrapping mechanism at the MoS_(2)/SiO_(2)interface.We demonstrate that perception under synergy is stronger than perception under optical or pressure signal alone,which is similar to a biological system.Moreover,various distinguishable motion scenarios(combination of the following conditions:external lighting environment of day or night,flat or rough road,movement state of walking or running)are simulated and verified by adjusting the amplitude and frequency of the optical and pressure signals.

A 27-mW 10-bit 125-MSPS charge domain pipelined ADC with a PVT insensitive boosted charge transfer circuit

A low power 10-bit 125-MSPS charge-domain(CD) pipelined analog-to-digital converter(ADC) based on MOS bucket-brigade devices(BBDs) is presented.A PVT insensitive boosted charge transfer(BCT) that is able to reject the charge error induced by PVT variations is proposed.With the proposed BCT,the common mode charge control circuit can be eliminated in the CD pipelined ADC and the system complexity is reduced remarkably.The prototype ADC based on the proposed BCT is realized in a 0.18μm CMOS process,with power consumption of only 27 mW at 1.8-V supply and active die area of 1.04 mm^2.The prototype ADC achieves a spurious free dynamic range(SFDR) of 67.7 dB,a signal-to-noise ratio(SNDR) of 57.3 dB,and an effective number of bits(ENOB) of 9.0 for a 3.79 MHz input at full sampling rate.The measured differential nonlinearity(DNL) and integral nonlinearity (INL) are +0.5/-0.3 LSB and +0.7/-0.55 LSB,respectively.

二维磁性VSe_(2)与过渡金属的范德华接触及其高性能自旋场效应晶体管研究

本文利用密度泛函理论和量子输运方法研究了过渡金属(TM):Fe、Co、Ni/2H-VSe_(2)杂化纳米结构的界面耦合和自旋输运特性.由于TM-Se-V的间接耦合作用导致体系的磁矩明显减小且2H-VSe_(2)半金属特性消失,所以预期的独立过渡金属、VSe_(2)的自旋过滤效果在接触区域变差.尽管如此,所有基于TM/2H-VSe_(2)的双端口器件仍呈现出一种有趣的偏压依赖自旋注入效率(SIE),其中Co/2H-VSe_(2)获得了非常可观的自旋输出电流:高达666 mA mm^(-1).进一步提出的基于过渡金属/2H-VSe_(2)的自旋场效应晶体管表现出出色的性能.在基于Ni/2H-VSe_(2)的晶体管中实现了非常高的自旋极化电流,高达3117 mA mm^(-1),器件同时还具有106 mV dec-1的开关特性.更为重要的是,所有晶体管在栅压的调控下,实现了自旋抽取效率(SEE)从96%到-92%连续可调,这些结果表明该器件有望应用于高性能自旋电子器件.

A digitally controlled AGC loop circuitry for GNSS receiver chip with a binary weighted accurate dB-linear PGA

A novel digitally controlled automatic gain control （AGC） loop circuitry for the global navigation satel- lite system （GNSS） receiver chip is presented. The entire AGC loop contains a programmable gain amplifier （PGA）, an AGC circuit and an analog-to-digital converter （ADC）, which is implemented in a 0.18 μm complementary metal--oxide-semiconductor （CMOS） process and measured. A binary-weighted approach is proposed in the PGA to achieve wide dB-linear gain control with small gain error. With binary-weighted cascaded amplifiers for coarse gain control, and parallel binary-weighted trans-conductance amplifier array for fine gain control, the PGA can provide a 64 dB dynamic range from -4 to 60 dB in 1.14 dB gain steps with a less than 0.15 dB gain error. Based on the Gaussian noise statistic characteristic of the GNSS signal, a digital AGC circuit is also proposed with low area and fast settling. The feed-backward AGC loop occupies an area of 0.27 mm^2 and settles within less than 165 μs while consuming an average current of 1.92 mA at 1.8 V.

A 10-bit 250 MSPS charge-domain pipelined ADC with replica controlled PVT insensitive BCT circuit

A low power 10-bit 250 MSPS charge-domain （CD） pipelined analog-to-digital converter （ADC） is introduced. The ADC is implemented in MOS bucket-brigade devices （BBDs） based CD pipelined architecture. A replica controlled boosted charge transfer （BCT） circuit is introduced to reject the influence of PVT variations on the charge transfer process. Based on replica controlled BCT, the CD pipelined ADC is designed and realized in a 1P6M 0.18μm CMOS process. The ADC achieves an SFDR of 64.4 dB, an SNDR of 56.9 dB and an ENOB of 9.2 for a 9.9 MHz input; and an SFDR of 63.1 dB, an SNR of 55.2 dB, an SNDR of 54.5 dB and an ENOB of 8.7 for a 220.5 MHz input at full sampling rate. The DNL is ＋0.5/- 0.55 LSB and INL is ＋0.8/- 0.85 LSB. The power consumption of the prototype ADC is only 45 mW at 1.8 V supply and it occupies an active die area of 1.56 mm2.

A low power time-interleaved 10-bit 250-MSPS charge domain pipelined ADC for IF sampling

A 10-bit 250-MSPS two-channel time-interleaved charge-domain（CD） pipelined analog-to-digital converter （ADC） is presented.MOS bucket-brigade device（BBD） based CD pipelined architecture is used to achieve low power consumption.An all digital low power DLL is used to alleviate the timing mismatches and to reduce the aperture jitter.A new bootstrapped MOS switch is designed in the sample and hold circuit to enhance the IF sampling capability.The ADC achieves a spurious free dynamic range（SFDR） of 67.1 dB,signal-to-noise ratio （SNDR） of 55.1 dB for a 10.1 MHz input,and SFDR of 61.6 dB,SNDR of 52.6 dB for a 355 MHz input at full sampling rate.Differential nonlinearity（DNL） is ＋0.5/-0.4 LSB and integral nonlineariry（INL） is ＋0.8/-0.75 LSB.Fabricated in a 0.18-μm 1P6M CMOS process,the prototype 10-bit pipelined ADC occupies 1.8×1.3 mm2 of active die area,and consumes only 68 mW at 1.8 V supply.

A 4 Gbps current-mode transmitter for 12-bit 250 MSPS ADC

A 4 Gbps transmitter for a 12-bit 250 MSPS pipelined ADCs is presented. A low power current mode （CM） output driver with reverse scaling technique is proposed. A high speed, low power combined serializer is implemented to convert 12 bit parallel data into a serial data stream. The whole transmitter is used in a 12-bit 250 MSPS pipelined ADC for the digital output buffer and fabricated in 180 nm 1.8 V 1PSM CMOS technology. Test results show that the transmitter provides an eye height greater than 800 mV for data rates of both 2 Gbps and 4 Gbps, the 12-bit 250 MSPS ADC achieves the SNR of 69.92 dBFS and SFDR of 81.17 dB with 20.1 MHz input at full sampling speed. The ADC with the 4 Gbps transmitter consumes the power consumption of 395 mW, where the power consumption of transmitter is 75 mW. The ADC occupies an area of 2.5 × 3.2 mm2, where the active area of the transmitter block is 0.5× 1.2 mm2.