Total Ionizing Dose Radiation Effects on MOS Transistors with Different Layouts

Both nMOS and pMOS transistors with two-edged and multi-finger layouts are fabricated in a standard commercial 0.6μm CMOS/bulk process to study their total ionizing dose （TID） radiation effects. The leakage current, threshold voltage shift, and transconductance of the devices are monitored before and after T-ray irradiation. Different device bias conditions are used during irradiation. The experiment results show that TID radiation effects on nMOS devices are very sensitive to their layout structures. The impact of the layout on TID effects on pMOS devices is slight and can be neglected.

The Bipolar Field-Effect Transistor:Ⅰ.Electrochemical Current Theory(Two-MOS-Gates on Pure-Base)

This paper describes the bipolar field-effect transistor （BiFET） and its theory. Analytical solution is ob- tained from partitioning the two-dimensional transistor into two one-dimensional transistors. The analysis employs the parametric surface-electric-potential and the electrochemical （quasi-Fermi） potential-gradient driving force to compute the current. Output and transfer D. C. current and conductance versus voltage are presented over practi- cal ranges of terminal D. C. voltages and device parameters. Electron and hole surface channel currents are pres- ent simultaneously, a new feature which could provide circuit functions in one physical transistor such as the CMOS inverter and SRAM memory.

The Bipolar Field-Effect Transistor: III.Short Channel Electrochemical Current Theory (Two-MOS-Gates on Pure-Base)

This paper describes the short channel theory of the bipolar field-effect transistor （BiFET） by partitioning the transistor into two sections,the source and drain sections,each can operate as the electron or hole emitter or collector under specific combinations of applied terminal voltages. Analytical solution is obtained in the source and drain sections by separating the two-dimensional trap-free Shockley Equations into two one-dimensional equations parametrically coupled via the surface-electric-potential and by using electron current continuity and hole current continuity at the boundary between the emitter and collector sections. Total and electron-hole-channel components of the output and transfer currents and conductances, and the electrical lengths of the two sections are computed and presented in graphs as a function of the D. C. terminal voltages for the model transistor with two identical and connected metal-oxide-silicon-gates （MOS-gates） on a thin pure-silicon base over practical ranges of thicknesses of the silicon base and gate oxide. Deviations of the long physical channel currents and conductances from those of the short electrical channels are reported.

The Bipolar Field-Effect Transistor:Ⅳ.Short Channel Drift-Diffusion Current Theory(Two-MOS-Gates on Pure-Base)

This paper gives the short channel analytical theory of the bipolar field-effect transistor （BiFET） with the drift and diffusion currents separately computed in the analytical theory. As in the last-month paper which represented the drift and diffusion current by the single electrochemical （potential-gradient） current, the two-dimensional transistor is partitioned into two sections, the source and drain sections, each can operate as the electron or hole emitter or collector under specific combinations of applied terminal voltages. Analytical solution is then obtained in the source and drain sections by separating the two-dimensional trap-free Shockley Equations into two one-dimensional equations parametrically coupled via the surface-electric-potential and by using electron current continuity and hole current continuity at the boundary between the emitter and collector sections. Total and the drift and diffusion components of the electron-channel and hole-channel currents and output and transfer conductances, and the electrical lengths of the two sections are computed and presented in graphs as a function of the D. C. terminal voltages for the model transistor with two identical and connected metal-oxide-silicon-gates （MOS-gates） on a thin pure-silicon base over practical ranges of thicknesses of the silicon base and gate oxide. Deviations of the two-section short-channel theory from the one-section long-channel theory are described.

The Theory of Field-Effect Transistors:XI. The Bipolar Electrochemical Currents(1-2-MOS-Gates on Thin-Thick Pure-Impure Base)

The field-effect transistor is inherently bipolar, having simultaneously electron and hole surface and volume channels and currents. The channels and currents are controlled by one or more externally applied transverse electric fields. It has been known as the unipolar field-effect transistor for 55-years since Shockley＇s 1952 invention,because the electron-current theory inevitably neglected the hole current from over-specified internal and boundary conditions, such as the electrical neutrality and the constant hole-electrochemical-potential, resulting in erroneous solutions of the internal and terminal electrical characteristics from the electron channel current alone, which are in gross error when the neglected hole current becomes comparable to the electron current, both in subthreshold and strong inversion. This report presents the general theory, that includes both electron and hole channels and currents. The rectangular （ x, y, z） parallelepiped transistors,uniform in the width direction （z-axis）,with one or two MOS gates on thin and thick,and pure and impure base, are used to illustrate the two-dimensional effects and the correct internal and boundary conditions for the electric and the electron and hole electrochemical potentials. Complete analytical equations of the DC current-voltage characteristics of four common MOS transistor structures are derived without over-specification： the 1-gate on semi-infinite-thick impure-base （the traditional bulk transistor）, the 1-gate on thin impure-silicon layer over oxide-insulated silicon bulk （SOI） ,the 1-gate on thin impure-silicon layer deposited on insulating glass （SOI TFT）, and the 2-gates on thin pure-base （FinFETs）.

The Bipolar Field-Effect Transistor:II.Drift-Diffusion Current Theory(Two-MOS-Gates on Pure-Base)

This paper describes the drift-diffusion theory of the bipolar field-effect transistor （BiFET） with two identical and connected metal-oxide-silicon-gates （MOS-gates） on a thin-pure-base. Analytical solution is obtained by partitioning the two-dimensional transistor into two one-dimensional problems coupled by the parametric sur- face-electric-potential. Total and component output and transfer currents and conductances versus D. C. voltages from the drift-diffusion theory, and their deviations from the electrochemical （quasi-Fermi） potential-gradient theory,are presented over practical ranges of thicknesses of the silicon base and gate oxide. A substantial contri- bution from the longitudinal gradient of the square of the transverse electric field is shown.

Study of total ionizing dose radiation effects on enclosed gate transistors in a commercial CMOS technology

This paper studies the total ionizing dose radiation effects on MOS （metal-oxide-semiconductor） transistors with normal and enclosed gate layout in a standard commercial CMOS （compensate MOS） bulk process. The leakage current, threshold voltage shift, and transconductance of the devices were monitored before and after γ-ray irradiation. The parameters of the devices with different layout under different bias condition during irradiation at different total dose are investigated. The results show that the enclosed layout not only effectively eliminates the leakage but also improves the performance of threshold voltage and transconductance for NMOS （n-type channel MOS） transistors. The experimental results also indicate that analogue bias during irradiation is the worst case for enclosed gate NMOS. There is no evident different behaviour observed between normal PMOS （p-type channel MOS） transistors and enclosed gate PMOS transistors.

Charge transport and quantum confinement in MoS2 dual-gated transistors

Semiconductive two dimensional(2D)materials have attracted significant research attention due to their rich band structures and promising potential for next-generation electrical devices.In this work,we investigate the MoS2 field-effect transistors(FETs)with a dual-gated(DG)architecture,which consists of symmetrical thickness for back gate(BG)and top gate(TG)dielectric.The thickness-dependent charge transport in our DG-MoS2 device is revealed by a four-terminal electrical measurement which excludes the contact influence,and the TCAD simulation is also applied to explain the experimental data.Our results indicate that the impact of quantum confinement effect plays an important role in the charge transport in the MoS2 channel,as it confines charge carriers in the center of the channel,which reduces the scattering and boosts the mobility compared to the single gating case.Furthermore,temperature-dependent transfer curves reveal that multi-layer MoS2 DG-FET is in the phonon-limited transport regime,while single layer MoS2 shows typical Coulomb impurity limited regime.

Improved performance of back-gate MoS2 transistors by NH3-plasma treating high-k gate dielectrics

NH3-plasma treatment is used to improve the quality of the gate dielectric and interface. Al2O3 is adopted as a buffer layer between HfO2 and MoS2 to decrease the interface-state density. Four groups of MOS capacitors and back-gate transistors with different gate dielectrics are fabricated and their C–V and I–V characteristics are compared. It is found that the Al2O3/HfO2 back-gate transistor with NH3-plasma treatment shows the best electrical performance: high on–off current ratio of 1.53 × 107, higher field-effect mobility of 26.51 cm2/V·s, and lower subthreshold swing of 145 m V/dec.These are attributed to the improvements of the gate dielectric and interface qualities by the NH3-plasma treatment and the addition of Al2O3 as a buffer layer.

SiC gate-controlled bipolar field effect composite transistor with polysilicon region for improving on-state current

A novel silicon carbide gate-controlled bipolar field effect composite transistor with poly silicon region(SiC GCBTP)is proposed.Different from the traditional electrode connection mode of SiC vertical diffused MOS(VDMOS),the P+region of P-well is connected with the gate in SiC GCBTP,and the polysilicon region is added between the P+region and the gate.By this method,additional minority carriers can be injected into the drift region at on-state,and the distribution of minority carriers in the drift region will be optimized,so the on-state current is increased.In terms of static characteristics,it has the same high breakdown voltage(811 V)as SiC VDMOS whose length of drift is 5.5μm.The on-state current of SiC GCBTP is 2.47×10^(-3)A/μm(V_(G)=10 V,V_(D)=10 V)which is 5.7 times of that of SiC IGBT and 36.4 times of that of SiC VDMOS.In terms of dynamic characteristics,the turn-on time of SiC GCBTP is only 0.425 ns.And the turn-off time of SiC GCBTP is similar to that of SIC insulated gate bipolar transistor(IGBT),which is 114.72 ns.

Trench MOS Controlled Thyristor

A new structure of power MOS-gated thyristor named Trench MOS Controlled Thyristor (TMCT) is presented.The MOSFETs used to turn on and turn off the thrysitor are formed with UMOS technology.No parasitic transistors exist in this structure,so the problems created by the parasitic transistors can be eliminated.So,the TMCT is expected to be of better performance.The experimental results of the multicellular 600V TMCT with the active area of 02mm2 show that the on-state drop is 125V at 300A/cm2,and the maximum controllable current reaches 296A/cm2 at the gate voltage of -20V and with an inductive load.

The Bipolar Theory of the Field-Effect Transistor:X.The Fundamental Physics and Theory(All Device Structures)

This paper describes the foundation underlying the device physics and theory of the semiconductor field effect transistor which is applicable to any devices with two carrier species in an electric field. The importance of the boundary conditions on the device current-voltage characteristics is discussed. An illustration is given of the transfer DCIV characteristics computed for two boundary conditions,one on electrical potential,giving much higher drift-limited parabolic current through the intrinsic transistor, and the other on the electrochemical potentials, giving much lower injection-over-thebarrier diffusion-limited current with ideal 60mV per decade exponential subthreshold roll-off, simulating electron and hole contacts. The two-MOS-gates on thin pure-body silicon field-effect transistor is used as examples

Field-effect transistors based on two-dimensional materials for logic applications

Field-effect transistors （FETs） for logic applications, graphene and MoS2, are discussed. These materials have based on two representative two-dimensional （2D） materials, drastically different properties and require different consider- ations. The unique band structure of graphene necessitates engineering of the Dirac point, including the opening of the bandgap, the doping and the interface, before the graphene can be used in logic applications. On the other hand, MoS2 is a semiconductor, and its electron transport depends heavily on the surface properties, the number of layers, and the carrier density. Finally, we discuss the prospects for the future developments in 2D material transistors.

Analysis and Characterization of Normally-Off Gallium Nitride High Electron Mobility Transistors

High electron mobility transistor(HEMT)based on gallium nitride(GaN)is one of the most promising candidates for the future generation of high frequencies and high-power electronic applications.This research work aims at designing and characterization of enhancement-mode or normally-off GaN HEMT.The impact of variations in gate length,mole concentration,barrier variations and other important design parameters on the performance of normally-off GaN HEMT is thoroughly investigated.An increase in the gate length causes a decrease in the drain current and transconductance,while an increase in drain current and transconductance can be achieved by increasing the concentration of aluminium(Al).For Al mole fractions of 23%,25%,and 27%,within Al gallium nitride(AlGaN)barrier,the GaN HEMT devices provide a maximum drain current of 347,408 and 474 mA/μm and a transconductance of 19,20.2,21.5 mS/μm,respectively.Whereas,for Al mole fraction of 10%and 15%,within AlGaN buffer,these devices are observed to provide a drain current of 329 and 283 mA/μm,respectively.Furthermore,for a gate length of 2.4,3.4,and 4.4μm,the device is observed to exhibit a maximum drain current of 272,235,and 221 mA/μm and the transconductance of 16.2,14,and 12.3 mS/μm,respectively.It is established that a maximum drain current of 997 mA/μm can be achieved with an Al concentration of 23%,and the device exhibits a steady drain current with enhanced transconductance.These observations demonstrate tremendous potential for two-dimensional electron gas(2DEG)for securing of the normally-off mode operation.A suitable setting of gate length and other design parameters is critical in preserving the normally-off mode operation while also enhancing the critical performance parameters at the same time.Due to the normallyon depletion-mode nature of GaN HEMT,it is usually not considered as suitable for high power levels,frequencies,and temperature.In such settings,a negative bias is required to enter the blocking condition;however,in the before-mentioned normally-off devices,the negative bias can be avoided and the channel can be depleted without applying a negative bias.

Design,modelling,and simulation of a floating gate transistor with a novel security feature

This study proposes a new generation of floating gate transistors(FGT)with a novel built-in security feature.The new device has applications in guarding the IC chips against the current reverse engineering techniques,including scanning capacitance microscopy(SCM).The SCM measures the change in the C–V characteristic of the device as a result of placing a minute amount of charge on the floating gate,even in nano-meter scales.The proposed design only adds a simple processing step to the conventional FGT by adding an oppositely doped implanted layer to the substrate.This new structure was first analyzed theoretically and then a two-dimensional model was extracted to represent its C–V characteristic.Furthermore,this model was verified with a simulation.In addition,the C–V characteristics relevant to the SCM measurement of both conventional and the new designed FGT were compared to discuss the effectiveness of the added layer in masking the state of the transistor.The effect of change in doping concentration of the implanted layer on the C–V characteristics was also investigated.Finally,the feasibility of the proposed design was examined by comparing its I–V characteristics with the traditional FGT.

Selective and localized laser annealing effect for high- performance flexible multilayer MoS2 thin-film transistors

We report the use of ultra-short, pulsed-laser annealed Ti/Au contacts to enhance the performance of multilayer MoS2 field effect transistors （FETs） on flexible plastic substrates without thermal damage. An analysis of the temperature distribution, based on finite difference methods, enabled understanding of the compatibility of our picosecond laser annealing for flexible poly（ethylene naphthalate） （PEN） substrates with low thermal budget （〈 200 ℃）. The reduced contact resistance after laser annealing provided a significant improvement in transistor performance including higher peak field-effect mobility （from 24.84 to 44.84 cm2-V-l.s-1）, increased output resistance （0.42 MΩ at Vgs- Vth = 20 V, a three-fold increase）, a six-fold increase in the self-gain, and decreased sub- threshold swing. Transmission electron microscopy analysis and current-voltage measurements suggested that the reduced contact resistance resulted from the decrease of Schottky barrier width at the MoS2-metal junction. These results demonstrate that selective contact laser annealing is an attractive technology for fabricating low-resistivity metal-semiconductor junctions, providing important implications for the application of high-performance two-dimensional semicon- ductor FETs in flexible electronics.

Construction of MoS2 field effect transistor sensor array for the detection of bladder cancer biomarkers

Bladder cancer is one of the commonest malignant tumors of urinary system with high recurrence. However, currently developed bladder cancer urine diagnosis methods are hindered by the low detection sensitivity and accuracy. Herein, a molybdenum disulfide(MoS2) nanosheets-based field effect transistor(FET) sensor array was constructed for simultaneous detection of multiple bladder cancer biomarkers in human urine. With the excellent electronic property of MoS2 and the high specific identification capability of recognition molecules, the proposed biosensor array could simultaneously detect nuclear matrix protein 22(NMP22) and cytokeratin 8(CK8) with a wide linear range of 10-6–10-1 pg mL-1 and an ultra-low detection limit of 0.027 and 0.019 aM, respectively. Furthermore, this highly sensitive and specific MoS2 FET sensor array could be used to identify bladder cancer biomarkers from human urine samples. This designed high-performance biosensor array shows great potential in the future diagnosis of bladder cancer.

Significant enhancement of photoresponsive characteristics and mobility of MoS2-based transistors through hybridization with perovskite CsPbBr3 quantum dots

Inorganic perovskite CsPbBr3 quantum dots (QDs) are potential nanoscale photosensitizers;moreover,two-dimensional (2-D) molybdenum disulfide (MoS2) has been intensively studied for application in the active layers of optoelectronic devices.In this study,heterostructures of 2D-monolayered MoS2 with zero-dimensional functionalized CsPbBr3 QDs were prepared,and their nanoscale optical characteristics were investigated.The effect of n-type doping on the MoS2 monolayer after hybridization with perovskite CsPbBr3 QDs was observed using laser confocal microscope photoluminescenca (PL) and Raman spectra.Field-effect transistors (FETs) using MoS2 and the MoS2-CsPbBr3 QDs hybrid were also fabricated,and their electrical and photoresponsive characteristics were investigated in terms of the charge transfer effect.For the MoS2-CsPbBr3 QDs-based FETs,the field effect mobility and photoresponsivity upon light irradiation were enhanced by ~ 4 times and a dramatic ~ 17 times,respectively,compared to the FET prepared without the parovskite QDs and without light irradiation.It is noteworthy that the photoresponsivity of the MoS-2-CsPbBr3 QDs-based FETs significantly increased with increasing light power,which is completely contrary to the behavior observed in previous studies of MoS2-based FETs.The increased mobility and significant enhancement of the photoresponsivity can be attributed to the n-type doping effect and efficient energy transfer from CsPbBr3 QDs to MoS2.The results indicate that the optoelectronic characteristics of MoS2-based FETs can be significantly improved through hybridization with photosensitive parovskite CsPbBr3 QDs.

Field-effect transistor with a chemically synthesized MoS2 sensing channel for label-free and highly sensitive electrical detection of DNA hybridization

A field-effect transistor （FET） with two-dimensional （2D） few-layer MoS2 as a sensing-channel material was investigated for label-free electrical detection of the hybridization of deoxyribonucleic acid （DNA） molecules. The high-quality MoS2-channel pattern was selectively formedthrough the chemical reaction of the Mo layer with H2S gas. The MoS2 FET was very stable in an electrolyte and inert to pH changes due to the lack of oxygen-containing functionalities on the MoS2 surface. Hybridization of single-stranded target DNA molecules with single-stranded probe DNA molecules physically adsorbed on the MoS2 channel resulted in a shift of the threshold voltage （Vt,） in the negative direction and an increase in the drain current. The negative shift in Vth is attributed to electrostatic gating effects induced by the detachment of negatively charged probe DNA molecules from the channel surface after hybridization. A detection limit of 10 fM, high sensitivity of 17 mWdec, and high dynamic range of 106 were achieved. The results showed that a bio-FET with an ultrathin 2D MoS2 channel can be used to detect very small concentrations of target DNA molecules specifically hybridized with the probe DNA molecules.

Enhancement of photoresponsive electrical characteristics of multilayer MoS2 transistors using rubrene patches

Multilayer MoS2 is a promising active material for sensing, energy harvesting, and optoelectronic devices owing to its intriguing tunable electronic band structure. However, its optoelectronic applications have been limited due to its indirect band gap nature. In this study, we fabricated a new type of phototransistor using multilayer MoS2 crystal hybridized with p-type organic semiconducting rubrene patches. Owing to the outstanding photophysical properties of rubrene, the device characteristics such as charge mobility and photoresponsivity were considerably enhanced to an extent depending on the thickness of the rubrene patches. The enhanced photoresponsive conductance was analyzed in terms of the charge results of the nanoscale laser confocal time-resolved PL measurements. transfer doping effect, validated by the microscope photoluminescence （PL） and