电磁脉冲对半导体器件的电流模式破坏

 利用时域有限差分（FDTD）方法,对电磁脉冲引起半导体器件的毁坏过程进行了数值模拟,得到了无负载半导体pn结器件在快前沿（ns量级）电磁脉冲作用下的瞬态行为,及由于电流引起的器件烧毁过程中器件参数的变化情况。     

Rapid laser fabrication of microlens array using colorless liquid photopolymer for AMOLED devices

Microlens array (MLA) is microfabricated using Ultra Violet (UV) laser for display device applications. A colorless liquid photopolymer, Norland Optical Adhesive (NOA) 60, is spin-coated and pre-cured via UV light for completing the laser process. The laser energy controlled by a galvano scanner is radiated on the surface of the NOA 60. A rapid thermal volume expansion inside the material creates microlens array when the Gaussian laser energy is absorbed. The fabrication process conditions for various shapes and densities of MLA using a non-contact surface profiler are investigated. Furthermore, we analyze the optical and display characteristics for the Organic Light Emitting Diode (OLED) devices. Optimized condition furnishes the OLED with the enhancement of light emission by 15%. We show that UV laser technique, which is installed with NOA 60 MLA layer, is eligible for improving the performance of the next generation display devices.     

A single-event transient induced by a pulsed laser in a silicon-germanium heterojunction bipolar transistor

A study on the single event transient (SET) induced by a pulsed laser in a silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) is presented in this work. The impacts of laser energy and collector load resistance on the SET are investigated in detail. The waveform, amplitude, and width of the SET pulse as well as collected charge are used to characterize the SET response. The experimental results are discussed in detail and it is demonstrated that the laser energy and load resistance significantly affect the SET in the SiGe HBT. Furthermore, the underlying physical mechanisms are analyzed and investigated, and a near-ideal exponential model is proposed for the first time to describe the discharge of laser-induced electrons via collector resistance to collector supply when both base-collector and collector-substrate junctions are reverse biased or weakly forward biased. Besides, it is found that an additional multi-path discharge would play an important role in the SET once the base-collector and collector-substrate junctions get strongly forward biased due to a strong transient step charge by the laser pulse.     

选择性埋氧层上硅器件的单粒子瞬态响应的温度相关性

本文建立了90 nm工艺下的绝缘体上硅浮体器件和选择性埋氧层上硅器件模型,通过器件电路混合仿真探究了工作温度对上述两种结构的多级反相器链单粒子瞬态脉冲宽度以及器件内部电荷收集过程的影响.研究表明, N型选择性埋氧层上硅器件相较于浮体器件具有更好的抗单粒子能力,但P型选择性埋氧层上硅器件的抗单粒子能力在高线性能量转移值下与浮体器件基本相同.同时电荷收集的温度相关性分析表明,N型选择性埋氧层上硅器件只存在漂移扩散过程,当温度升高时其电荷收集量变化很小,而N型浮体器件存在双极放大过程,电荷收集量随着温度的升高而显著增加;另外, P型选择性埋氧层上硅器件和浮体器件均存在双极放大过程,当温度升高时P型选择性埋氧层上硅器件衬底中的双极放大过程越来越严重,由于局部埋氧层的存在,反而抑制了其源极的双极放大过程,导致它的电荷收集量要明显少于P型浮体器件.因此选择性埋氧层上硅器件比浮体器件更好地抑制了温度对单粒子瞬态脉冲的影响.     

Single-electron tunneling and Coulomb blockade in carbon-based quantum dots

Single-electron tunneling (SET) and Coulomb blockade (CB) phenomena have been widely observed in nanoscaled electronics and have received intense attention around the world. In the past few years, we have studied SET in carbon nanotube fragments and fullerenes by applying the so-called “Orthodox” theory [28]. As outlined in this review article, we investigated the single-electron charging and discharging process via current-voltage characteristics, gate effect, and electronic structure-related factors. Because the investigated geometric structures are three-dimensionally confined, resulting in a discrete spectrum of energy levels resembling the property of quantum dots, we evidenced the CB and Coulomb staircases in these structures. These nanostructures are sufficiently small that introducing even a single electron is sufficient to dramatically change the transport properties as a result of the charging energy associated with this extra electron. We found that the Coulomb staircases occur in the I–V characteristics only when the width of the left barrier junction is smaller than that of the right barrier junction. In this case, the transmission coefficient of the emitter junction is larger than that of the collector junction; also, occupied levels enter the bias window, thereby enhancing the tunneling extensively.      

纳米体硅鳍形场效应晶体管单粒子瞬态中的源漏导通现象

体硅鳍形场效应晶体管(FinFET)是晶体管尺寸缩小到30 nm以下应用最多的结构,其单粒子瞬态产生机理值得关注.利用脉冲激光单粒子效应模拟平台开展了栅长为30, 40, 60, 100 nm Fin FET器件的单粒子瞬态实验,研究FinFET器件单粒子瞬态电流脉冲波形随栅长变化情况;利用计算机辅助设计(technology computer-aided design, TCAD)软件仿真比较电流脉冲产生过程中器件内部电子浓度和电势变化,研究漏电流脉冲波形产生的物理机理.研究表明,不同栅长Fin FET器件瞬态电流脉冲尾部都存在明显的平台区,且平台区电流值随着栅长变短而增大;入射激光在器件沟道区下方体区产生高浓度电子将源漏导通产生导通电流,而源漏导通升高了体区电势,抑制体区高浓度电子扩散,使得导通状态维持时间长,形成平台区电流;尾部平台区由于持续时间长,收集电荷量大,会严重影响器件工作状态和性能.研究结论为纳米Fin FET器件抗辐射加固提供理论支撑.     

Fabrication and characterization of 1.55 μm single transverse mode large diameter electrically pumped VECSEL

We report on the design, fabrication, and characterization of InP-based 1.55 μm wavelength large diameter (50 μm) electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). The hybrid device consists of a half vertical cavity surface emitting laser (1/2-VCSEL) structure assembled with a concave dielectric external mirror. The 1/2-VCSEL is monolithically grown on InP substrate and includes a semiconductor Bragg mirror and a tunnel junction for electrical injection. Buried (BTJ) and ion implanted (ITJ) tunnel junction electrical confinement schemes are compared in terms of their thermal and electrical characteristics. Lower thermal resistance values are measured for BJT, but reduced current crowding effects and uniform current injection are evidenced for ITJ. Using the ITJ technique, we demonstrate Room-Temperature (RT) continuous-wave (CW) single transverse mode laser operation from 50-μm diameter EP-VECSEL devices. We show that the experimental laser optical output versus injected current (L–I) curves are well-reproduced by a simple analytical thermal model, consistent with the thermal resistance measurements performed on the 1/2-VCSEL structure. Our results indicate that thermal heating is the main mechanism limiting the maximum CW output power of 50-μm diameter VECSELs, rather than current injection inhomogeneity.     

Si doping in Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript> film to reduce the writing current of phase change memory

The characteristics of phase change memory devices in size of several micrometers and with pure Ge₂Sb₂Te₅ (GST), N-doped GST, and Si-doped GST films were investigated and compared with each other. The Si-doped GST device can perform SET and RESET cycles, even if the Si dopant is as small as 4.1 at. %. But the GST and N-doped GST device cannot perform the RESET process, though the SET state resistance of N-doped device is almost the same as that of Si-doped device and larger than that of GST device. In order to explain this phenomenon, the electrical and DSC characteristics of three kinds of films were investigated. Phase separation was found in Si-doped GST films. The reason of the RESET ability of Si-doped GST devices is supposed to be the existence of rich Si phases which act as micro-heaters. Thermal conduction simulations confirmed this supposition and indicate that the separated high resistance phase (rich Si phase) can heat the active volume of device efficiently and reduce the writing current largely. PACS 71.55.Gs; 71.55.Jv; 74.81.Bd; 85.30-z     

瞬态光电流对有机薄膜光伏器件中肖特基接触的研究

制备了结构为氧化铟锡(ITO)/有机半导体/金属的有机薄膜光伏器件,电流--电压曲线显示其具有整流特性但有机半导体和电极间肖特基接触的内建电场方向很难判定.为了研究有机半导体和电极的肖特基接触特性,分别制备了结构为ITO/有机绝缘层/有机半导体/金属和ITO/有机半导体/有机绝缘层/金属的器件,通过调制激光照射下器件的瞬态光电流方向可容易判断有机半导体和电极间肖特基接触的内建电场方向,外加偏压下瞬态光电流的强度变化进一步证实了判断的正确性.     

Simulation of SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling

A three-dimensional finite element model for phase change random access memory （PCRAM） is established for comprehensive electrical and thermal analysis during SET operation. The SET behaviours of the heater addition structure （HS） and the ring-type contact in bottom electrode （RIB） structure are compared with each other. There are two ways to reduce the RESET current, applying a high resistivity interracial layer and building a new device structure. The simulation resuIts indicate that the variation of SET current with different power reduction ways is little. This study takes the RESET and SET operation current into consideration, showing that the RIB structure PCRAM cell is suitable for future devices with high heat efficiency and high-density, due to its high heat efficiency in RESET operation.     

Small-signal modeling of graphene barristors

This paper presents a small-signal model for graphene barristor, a promising device for the future nanoelectronics industry. Because of the functional similarities to the conventional FET transistors, the same configuration and parameters, as those of FETs, are assumed for the model. Transconductance, output resistance, and parasitic capacitances are the main parameters of the small signal equivalent circuit modeled in this work. Recognizing the importance of physical modeling of novel semiconductor devices, we develop physical compact expressions for the device radio-frequency characteristics. Furthermore, we clarify the physics behind the variation of the characteristics as the device parameters change. We also validate our model results with available simulation results. Impact of equilibrium Schottky barrier height of the graphene–silicon junction on the radio frequency performance of barristor is investigated, too.     

Effect of electrical contact on performance of WSe2 field effect transistors

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) such as tungsten diselenide (WSe₂) have spead many interesting physical properties, which may become ideal candidates to develop new generation electronic and optoelectronic devices. In order to reveal essential features of 2D TMDCs, it is necessary to fabricate high-quality devices with reliable electrical contact. We systematically analyze the effect of graphene and metal contacts on performance of multi-layered WSe₂ field effect transistors (FETs). The temperature-dependent transport characteristics of both devices are tested. Only graphene-contacted WSe₂ FETs are observed with the metal-insulator transition phenomenon which mainly attributes to the ultra-clean contact interface and lowered contact barrier. Further characterization on contact barrier demonstrates that graphene contact enables lower contact barrier with WSe₂ than metal contact, since the Fermi level of graphene can be modulated by the gate bias to match the Fermi level of the channel material. We also analyze the carrier mobility of both devices under different temperatures, revealing that graphene contact can reduce the charge scattering of the device caused by ionized impurities and phonon vibrations in low and room temperature regions, respectively. This work is expected to provide reference for fabricating 2D material devices with decent performances.     

Dynamic thermal modeling and parameter identification for a monolithic laser diode module

We improved the thermal equivalent-circuit model of the laser diode module(LDM) to evaluate its thermal dynamic properties and calculate the junction temperature of the laser diode with a high accuracy.The thermal parameters and the transient junction temperature of the LDM are modeled and obtained according to the temperature of the thermistor integrated in the module.Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines,and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.     

Dynamic thermal modeling and parameter identification for monolithic laser diode module

We improve the thermal equivalent-circuit model of the laser diode module (LDM) to evaluate its thermal dynamic property and calculate the junction temperature of the laser diode with a high accuracy. The thermal parameters and the transient junction temperature of LDM are modeled and obtained according to the temperature of the thermistor integrated in the module. Our improved thermal model is verified indirectly by monitoring the emission wavelength of the laser diode against gas absorption lines, and several thermal parameters are obtained with the temperature uncertainty of 0.01 K in the thermal dynamic process.     

Operational and design considerations for broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition for high power applications

Graded barrier quantum well heterostructure (GBQWH) broad area lasers have been shown to be capable of high power pulsed and cw operation. In this article, we consider several operational characteristics and design issues associated with broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition. In particular, the effect of junction heating on emission wavelength for cw device operation and the effects of various buffer layer structures on the material properties and device characteristics of GBQWH structures are addressed. Typical results for high power operation of uncoated broad area laser diodes are also outlined.     

Operational and design considerations for broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition for high power applications

Graded barrier quantum well heterostructure (GBQWH) broad area lasers have been shown to be capable of high power pulsed and cw operation. In this article, we consider several operational characteristics and design issues associated with broad area graded barrier quantum well heterostructure lasers grown by metalorganic chemical vapor deposition. In particular, the effect of junction heating on emission wavelength for cw device operation and the effects of various buffer layer structures on the material properties and device characteristics of GBQWH structures are addressed. Typical results for high power operation of uncoated broad area laser diodes are also outlined.     

Boundary field theory approach to the renormalization of SQUID devices

We show that the quantum properties of some Josephson SQUID devices are described by a boundary sine-Gordon model. Our approach naturally describes multi-junction SQUID devices and, when applied to a single junction SQUID (the rf-SQUID), it reproduces the known results of Glazman and Hekking. We provide a detailed analysis of the regimes accessible to an rf-SQUID and to a two-Josephson junction SQUID device (the dc-SQUID). We then compute the normal component of the current-response of a SQUID device to an externally applied voltage and show that the equation describing the current-voltage characteristic function reduces to well-known results when the infrared cutoff is suitably chosen. Our approach helps in establishing new and interesting connections between superconducting devices, quantum Brownian motion, fermionic quantum wires and, more generally, quantum impurity problems.     

锗硅异质结晶体管单粒子效应激光微束模拟

对国产锗硅异质结双极晶体管(SiGe HBT)进行了单粒子效应激光微束辐照试验,观测SiGe HBT单粒子效应的敏感区域,测试不同外加电压和不同激光能量下SiGe HBT集电极瞬变电流和电荷收集情况,并结合器件结构对试验结果进行分析。试验结果表明:国产SiGe HBT位于集电极/衬底结内的区域对单粒子效应敏感,波长为1064 nm的激光在能量约为1.5 nJ时诱发SiGe HBT单粒子效应,引起电流瞬变。入射激光能量增强,电流脉冲增大,电荷收集量增加;外加电压增大,电流脉冲的波峰增大;SiGe HBT的单粒子效应与外加电压大小和入射激光能量都相关,电压主要影响瞬变电流的峰值,而电荷收集量主要依赖于入射激光能量。     

Influence of linker molecules on charge transport through self-assembled single-nanoparticle devices

We investigate electrical characteristics of single-electron electrode/nanoisland/electrode devices formed by alkanedithiol assisted self-assembly. Contrary to predictions of the orthodox model for double tunnel junction devices, we find a significant ( approximately fivefold) discrepancy in single-electron charging energies determined by Coulomb blockade (CB) voltage thresholds in current-voltage measurements versus those determined by an Arrhenius analysis of conductance in the CB region. The energies do, however, scale with particle sizes, consistent with single-electron charging phenomena. We propose that the discrepancy is caused by a multibarrier junction potential that leads to a voltage divider effect. Temperature and voltage dependent conductance measurements performed outside the blockade region are consistent with this picture. We simulated our data using a suitably modified orthodox model.     

Flexible and degradable resistive switching memory fabricated with sodium alginate

Transient electronics has attracted interest as an emerging technology to solve electronic-waste problem,due to its physically vanishing ability in solution.Here in this work,we demonstrate a flexible and degradable transient resistive switching(RS) memory device with simple structure of Cu/sodium alginate(SA)/ITO.The device presents excellent RS characteristics as well as high flexibility,including low operating voltage(1.5 V) and multilevel RS behavior.No performance degradation occurs after bending the device 50 times.Moreover,our device can be absolutely dissolved in deionized water.The proposed SA-based transient memory device has great potential for the development of green and security memory devices.