Single event effect in a ferroelectric-gate field-effect transistor under heavy-ion irradiation

The single event effect in ferroelectric-gate field-effect transistor （FeFET） under heavy ion irradiation is investigated in this paper. The simulation results show that the transient responses are much lower in a FeFET than in a conventional metal-oxide-semiconductor field-effect transistor （MOSFET） when the ion strikes the channel. The main reason is that the polarization-induced charges （the polarization direction here is away from the silicon surface） bring a negative surface po- tential which will affect the distribution of carders and charge collection in different electrodes significantly. The simulation results are expected to explain that the FeFET has a relatively good immunity to single event effect.     

Utilizing a shallow trench isolation parasitic transistor to characterize the total ionizing dose effect of partially-depleted silicon-on-insulator input/output n-MOSFETs

We investigate the effects of 60 Co γ-ray irradiation on the 130 nm partially-depleted silicon-on-isolator(PDSOI)input/output(I/O) n-MOSFETs. A shallow trench isolation(STI) parasitic transistor is responsible for the observed hump in the back-gate transfer characteristic curve. The STI parasitic transistor, in which the trench oxide acts as the gate oxide,is sensitive to the radiation, and it introduces a new way to characterize the total ionizing dose(TID) responses in the STI oxide. A radiation enhanced drain induced barrier lower(DIBL) effect is observed in the STI parasitic transistor. It is manifested as the drain bias dependence of the radiation-induced off-state leakage and the increase of the DIBL parameter in the STI parasitic transistor after irradiation. Increasing the doping concentration in the whole body region or just near the STI sidewall can increase the threshold voltage of the STI parasitic transistor, and further reduce the radiation-induced off-state leakage. Moreover, we find that the radiation-induced trapped charge in the buried oxide leads to an obvious front-gate threshold voltage shift through the coupling effect. The high doping concentration in the body can effectively suppress the radiation-induced coupling effect.     

Total Ionizing Dose Response of Different Length Devices in 0.13 μm Partially Depleted Silicon-on-Insulator Technology

An anomalous total dose effect that the long length device is more susceptible to total ionizing dose than the short one is observed with the 0.13 μm partially depleted silicon-on-insulator technology. The measured results and 3 D technology computer aided design simulations demonstrate that the devices with different channel lengths may exhibit an enhanced reverse short channel effect after radiation. It is ascribed to that the halo or pocket implants introduced in processes results in non-uniform channel doping profiles along the device length and trapped charges in the shallow trench isolation regions.     

A New silicon—on—Insulator Structure of Metal—Oxide—Semiconductor Field Effect Transistor to Reduce Self—Heating Effect

A new silicon-on-insulator(SOI)device stucture is proposed.This new design provides a new path to reduce the temperature of the channel of SOI metal-oxide-semiconductor field effect transistor(MOSFET).The device has been verified in two-dimensional device simulation,The new structure reduces the self-heating effect of SOI MOSFET and decreases the negative differential transconductance.     

Corner effects in double-gate/gate-all-around MOSFETs

Two kinds of corner effects existing in double-gate (DG) and gate-all-around (GAA) MOSFETs have been investigated by three-dimensional (3D) and two-dimensional (2D) simulations. It is found that the corner effect caused by conterminous gates, which is usually deemed to deteriorate the transistor performance, does not always play a negative role in GAA transistors. It can suppress the leakage current of transistors with low channel doping, though it will enhance the leakage current at high channel doping. The study of another kind of corner effect, which exists in the corner at the bottom of the silicon pillar of DG/GAA vertical MOSFETs, indicates that the D-top structure with drain on the top of the device pillar of vertical transistor shows great advantage due to lower leakage current and better DIBL (drain induced barrier lowering) effect immunity than the S-top structure with source on the top of the device pillar. Therefore the D-top structure is more suitable when the requirement in leakage current and short channel character is critical.     

Electrical characteristics of AlInN/GaN HEMTs under cryogenic operation

Electrical properties of an AlInN/GaN high-electron mobility transistor (HEMT) on a sapphire substrate are investi-gated in a cryogenic temperature range from 295 K down to 50 K. It is shown that drain saturation current and conductance increase as transistor operation temperature decreases. A self-heating effect is observed over the entire range of temperature under high power consumption. The dependence of channel electron mobility on electron density is investigated in detail. It is found that aside from Coulomb scattering, electrons that have been pushed away from the AlInN/GaN interface into the bulk GaN substrate at a large reverse gate voltage are also responsible for the electron mobility drop with the decrease of electron density.     

Gas flow characteristics in straight silicon microchannels

Experiments have been conducted to investigate nitrogen gas flow characteristics through four trapezoidal silicon microchannels with different hydraulic diameters. The volume flow rate and pressure ratio are measured in the experiments. It is found that the friction coefficient is no longer a constant, which is different from the conventional theory. The characteristics are first explained by the theoretical analysis. A simplified rectangular model (rectangular straight channel model) is then proposed. The experimental results are compared with the theoretical predictions based on the simplified rectangular model and the two-dimensional flow between the parallel-plate model which was usually used. The difference between the experimental data and the theoretical predictions is found in the high-pressure ratio cases. The influence of the gas compressibility effect based on the Boltzmann gas kinetic analysis method is studied to interpret the discrepancy. We discuss two important factors affecting the application extent of different prediction models.     

Hot carrier degradation and a new lifetime prediction model in ultra-deep sub-micron pMOSFET

The hot carrier effect (HCE) of an ultra-deep sub-micron p-channel metal-oxide semiconductor field-effect transistor (pMOSFET) is investigated in this paper. Experiments indicate that the generation of positively charged interface states is the predominant mechanism in the case of the ultra-deep sub-micron pMOSFET. The relation of the pMOSFET hot carrier degradation to stress time (t), channel width (W ), channel length (L), and stress voltage (Vd ) is then discussed. Based on the relation, a lifetime prediction model is proposed, which can predict the lifetime of the ultra-deep sub-micron pMOSFET accurately and reflect the influence of the factors on hot carrier degradation directly.     

Anisotropic self-diffusion of fluorinated poly(methacrylate) in metal-organic frameworks assessed with molecular dynamics simulation

Utilizing the periodically structured metal–organic framework(MOF) as the reaction vessel is a promising technique to achieve the aligned polymer molecular chains, where the diffusion procedure of the polymer monomer inside MOF is one of the key mechanisms. To investigate the diffusion mechanism of fluorinated polymer monomers in MOFs, in this paper the molecular dynamics simulations combined with the density functional theory and the Monte Carlo method are used and the all-atom models of TFMA(trifluoroethyl methacrylate) monomer and two types of MOFs, [Zn_2(BDC)_2(TED)]n and[Zn_2(BPDC)_2(TED)]n, are established. The diffusion behaviors of TFMA monomer in these two MOFs are simulated and the main influencing factors are analyzed. The obtained results are as follows. First, the electrostatic interactions between TFMA monomers and MOFs cause the monomers to concentrate in the MOF channel, which slows down the monomer diffusion. Second, the anisotropic shape of the one-dimensional MOF channel leads to different diffusion speeds of monomers in different directions. Third, MOF with a larger pore diameter due to a longer organic ligand, [Zn_2(BPDC)_2(TED)]n in this paper, facilitates the diffusion of monomers in the MOF channel. Finally, as the number of monomers increases, the self-diffusion coefficient is reduced by the steric effect.     

Early effect modeling of silicon-on-insulator SiGe heterojunction bipolar transistors

Silicon germanium(SiGe) heterojunction bipolar transistor(HBT) on thin silicon-on-insulator(SOI) has recently been demonstrated and integrated into the latest SOI BiCMOS technology.The Early effect of the SOI SiGe HBT is analysed considering vertical and horizontal collector depletion,which is different from that of a bulk counterpart.A new compact formula of the Early voltage is presented and validated by an ISE TCAD simulation.The Early voltage shows a kink with the increase of the reverse base-collector bias.Large differences are observed between SOI devices and their bulk counterparts.The presented Early effect model can be employed for a fast evaluation of the Early voltage and is useful to the design,the simulation and the fabrication of high performance SOI SiGe devices and circuits.     

Dual-Material Surrounding-Gate Metal-Oxide-Semiconductor Field Effect Transistors with Asymmetric Halo

Asymmetrical halo and dual-material gate structure are used in the sub-100 nm surrounding-gate metal oxidesemiconductor field effect transistor （MOSFET） to improve the performance. Using three-region parabolic potential distribution and universal boundary condition, analytical surface potential and threshold voltage models of the novel MOSFET are developed based on the solution of Poisson＇s equation. The performance of the MOS- FET is examined by the analytical models and the 3D numerical device simulator Davinci. It is shown that the novel MOSFET can suppress short channel effect and improve carrier transport efficiency. The derived analytical models agree well with Davinci.     

Mechanisms of atmospheric neutron-induced single event upsets in nanometric SOI and bulk SRAM devices based on experiment-verified simulation tool

In this paper, a simulation tool named the neutron-induced single event effect predictive platform(NSEEP~2) is proposed to reveal the mechanism of atmospheric neutron-induced single event effect(SEE) in an electronic device, based on heavy-ion data and Monte-Carlo neutron transport simulation. The detailed metallization architecture and sensitive volume topology of a nanometric static random access memory(SRAM) device can be considered to calculate the real-time soft error rate(RTSER) in the applied environment accurately. The validity of this tool is verified by real-time experimental results. In addition, based on the NSEEP~2, RTSERs of 90 nm–32 nm silicon on insulator(SOI) and bulk SRAM device under various ambient conditions are predicted and analyzed to evaluate the neutron SEE sensitivity and reveal the underlying mechanism. It is found that as the feature size shrinks, the change trends of neutron SEE sensitivity of bulk and SOI technologies are opposite, which can be attributed to the different MBU performances. The RTSER of bulk technology is always 2.8–64 times higher than that of SOI technology, depending on the technology node, solar activity, and flight height.     

Magnetocaloric and magnetic properties of La_2NiMnO_6 double perovskite

The magnetic effect and the magnetocaloric effect in La_2NiMnO_6(LNMO) double perovskite are studied using the Monte Carlo simulations.The magnetizations,specific heat values,and magnetic entropies are obtained for different exchange interactions and external magnetic fields.The adiabatic temperature is obtained.The transition temperature is deduced.The relative cooling power is established with a fixed value of exchange interaction.According to the master curve behaviors for the temperature dependence of △S_m~(max) predicted for different maximum fields,in this work it is confirmed that the paramagnetic-ferromagnetic phase transition observed for our sample is of a second order.The near room-temperature interaction and the superexchange interaction between Ni and Mn are shown to be due to the ferromagnetism of LNMO.     

Simulation of grain boundary effect on characteristics of ZnO thin film transistor by considering the location and orientation of grain boundary

The grain boundaries (GBs) have a strong effect on the electric properties of ZnO thin film transistors (TFTs). A novel grain boundary model was developed to analyse the effect. The model was characterized with different angles between the orientation of the grain boundary and the channel direction. The potential barriers formed by the grain boundaries increase with the increase of the grain boundary angle, so the degradation of the transistor characteristics increases. When a grain boundary is close to the drain edge, the potential barrier height reduces, so the electric properties were improved.     

Transient simulation and analysis of current collapse due to trapping effects in AlGaN/GaN high-electron-mobility transistor

In this paper, two-dimensional(2D) transient simulations of an Al Ga N/Ga N high-electron-mobility transistor(HEMT)are carried out and analyzed to investigate the current collapse due to trapping effects. The coupling effect of the trapping and thermal effects are taken into account in our simulation. The turn-on pulse gate-lag transient responses with different quiescent biases are obtained, and the pulsed current–voltage(I–V) curves are extracted from the transients. The experimental results of both gate-lag transient current and pulsed I–V curves are reproduced by the simulation, and the current collapse due to the trapping effect is explained from the view of physics based on the simulation results. In addition, the results show that bulk acceptor traps can influence the gate-lag transient characteristics of Al Ga N/Ga N HEMTs besides surface traps and that the thermal effect can accelerate the emission of captured electrons for traps. Pulse transient simulation is meaningful in analyzing the mechanism of dynamic current collapse, and the work in this paper will benefit the reliability study and model development of Ga N-based devices.     

Multifunctional silicon-based light emitting device in standard complementary metal–oxide–semiconductor technology

A three-terminal silicon-based light emitting device is proposed and fabricated in standard 0.35 μ m complementary metal--oxide--semiconductor technology. This device is capable of versatile working modes: it can emit visible to near infra-red (NIR) light (the spectrum ranges from 500 nm to 1000 nm) in reverse bias avalanche breakdown mode with working voltage between 8.35 V--12 V and emit NIR light (the spectrum ranges from 900 nm to 1300 nm) in the forward injection mode with working voltage below 2 V. An apparent modulation effect on the light intensity from the polysilicon gate is observed in the forward injection mode. Furthermore, when the gate oxide is broken down, NIR light is emitted from the polysilicon/oxide/silicon structure. Optoelectronic characteristics of the device working in different modes are measured and compared. The mechanisms behind these different emissions are explored.     

Parasitic bipolar amplification in a single event transient and its temperature dependence

Using three-dimensional technology computer-aided design (TCAD) simulation, parasitic bipolar amplification in a single event transient (SET) current of a single transistor and its temperature dependence are studied. We quantify the contributions of different current components in a SET current pulse, and it is found that the proportion of parasitic bipolar amplification in total collected charge is about 30% in both 130-nm and 90-nm technologies. The temperature dependence of parasitic bipolar amplification and the mechanism of the SET pulse are also investigated and quantified. The results show that the proportion of charge induced by parasitic bipolar increases with rising temperature, which illustrates that the parasitic bipolar amplification plays an important role in the charge collection of a single transistor.     

Electrohydromechanical analysis based on conductivity gradient in microchannel

Fluid manipulation is very important in any lab-on-a-chip system. This paper analyses phenomena which use the alternating current （AC） electric field to deflect and manipulate coflowing streams of two different electrolytes （with conductivity gradient） within a microfluidic channel. The basic theory of the electrohydrodynamics and simulation of the analytical model are used to explain the phenomena. The velocity induced for different voltages and conductivity gradient are computed. The results show that when the AC electrical signal is applied on the electrodes, the fluid with higher conductivity occupies a larger region of the channel and the interface of the two fluids is deflected. It will provide some basic reference for people who want to do more study in the control of different fluids with conductivity gradient in a microfluidic channel.     

Effect of radiation-induced mean wavelength shift in optical fibers on the scale factor of an interferometric fiber optic gyroscope at a wavelength of 1300 nm

In order to analyze the effect of wavelength-dependent radiation-induced attenuation (RIA) on the mean trans- mission wavelength in optical fiber and the scale factor of interferometric fiber optic gyroscopes (IFOGs), three types of polarization-maintaining (PM) fibers are tested by using a 60 Co γ-radiation source. The observed different mean wave- length shift (MWS) behaviors for different fibers are interpreted by color-center theory involving dose rate-dependent absorption bands in ultraviolet and visible ranges and total dose-dependent near-infrared absorption bands. To evaluate the mean wavelength variation in a fiber coil and the induced scale factor change for space-borne IFOGs under low radiation doses in a space environment, the influence of dose rate on the mean wavelength is investigated by testing four germanium (Ge) doped fibers and two germanium-phosphorus (Ge-P) codoped fibers irradiated at different dose rates. Experimental results indicate that the Ge-doped fibers show the least mean wavelength shift during irradiation and their mean wavelength of optical signal transmission in fibers will shift to a shorter wavelength in a low-dose-rate radiation environment. Finally, the change in the scale factor of IFOG resulting from the mean wavelength shift is estimated and tested, and it is found that the significant radiation-induced scale factor variation must be considered during the design of space-borne IFOGs.     

Degradation of gate-recessed MOS-HEMTs and conventional HEMTs under DC electrical stress

The performance degradation of gate-recessed metal–oxide–semiconductor high electron mobility transistor(MOSHEMT) is compared with that of conventional high electron mobility transistor(HEMT) under direct current(DC) stress,and the degradation mechanism is studied. Under the channel hot electron injection stress, the degradation of gate-recessed MOS-HEMT is more serious than that of conventional HEMT devices due to the combined effect of traps in the barrier layer, and that under the gate dielectric of the device. The threshold voltage of conventional HEMT shows a reduction under the gate electron injection stress, which is caused by the barrier layer traps trapping the injected electrons and releasing them into the channel. However, because of defects under gate dielectrics which can trap the electrons injected from gate and deplete part of the channel, the threshold voltage of gate-recessed MOS-HEMT first increases and then decreases as the conventional HEMT. The saturation phenomenon of threshold voltage degradation under high field stress verifies the existence of threshold voltage reduction effect caused by gate electron injection.