Radiation effects on MOS and bipolar devices by 8 MeV protons,60 MeV Br ions and 1 MeV electrons

The radiation effects of the metal-oxide-semiconductor （MOS） and the bipolar devices are characterised using 8 MeV protons, 60 MeV Br ions and 1 MeV electrons. Key parameters are measured in-situ and compared for the devices. The ionising and nonionising energy losses of incident particles are calculated using the Geant4 and the stopping and range of ions in matter code. The results of the experiment and energy loss calculation for different particles show that different incident particles may give different contributions to MOS and bipolar devices. The irradiation particles, which cause a larger displacement dose within the same chip depth of bipolar devices at a given total dose, would generate more severe damage to the voltage parameters of the bipolar devices. On the contrary, the irradiation particles, which cause larger ionising damage in the gate oxide, would generate more severe damage to MOS devices. In this investigation, we attempt to analyse the sensitivity to radiation damage of the different parameter of the MOS and bipolar devices by comparing the irradiation experimental data and the calculated results using Geant4 and SRIM code.

Properties of a MOS Device on Single Layer Molybdenum Disulfide

The properties of a metal-oxide-semiconductor device on a single layer MoS_(2)(molybdenum disulfide)semiconductor are determined theoretically utilizing the concept of physics that the carrier effective masses in materials are related to the intrinsic Fermi energy levels in materials by the universal mass-energy equivalence equation given as dE/E=dm/m,where E is the energy and m is the mass of the free electron.The known parameters of electron effective mass of 0.48 m and the direct bandgap of 1.8 eV for monolayer MoS_(2) semiconductor are utilized to determine the properties of the MOS(metal-oxide-semiconductor)device,with the given previous research consequence that the threshold for electron heating in SiO_(2) is 2 MV/cm-eV.

Sinusoidal Steady State Analysis on 4H-SiC Buried Channel MOSFETs

With the combined use of the drift-diffusion （DD） model, experiment measured parameters and small-signal sinusoidM steady-state analysis, we extract the Y-parameters for 4H-SiC buried-channel metal oxide semicon- ductor field effect transistors （BCMOSFETs）. Output short-circuit current gain G and Mason＇s invariant U are cMculated for extrapolating unity current gain frequency in the common-source configuration fT and the maximum frequency of oscillation fmax, respectively. Here fT = 800 MHz and fmax= 5 GHz are extracted for the 4H-SiC BCMOSFETs, while the field effect mobility reaches its peak value 87cm2/Vs when VGs = 4.5 V. Simulation results clearly show that the characteristic frequency of 4H-SiC BCMOSFETs and field effect mobility are superior, due to the novel structure, compared with conventional MOSFETs.

Improved interfacial properties of HfGdON gate dielectric Ge MOS capacitor by optimizing Gd content

High-quality dielectric/Ge interface and low gate leakage current are crucial issues for high-performance nanoscaled Ge-based complementary metal–oxide–semiconductor(CMOS) device. In this paper, the interfacial and electrical properties of high-k Hf Gd ON/La Ta ON stacked gate dielectric Ge metal–oxide–semiconductor(MOS) capacitors with different gadolinium(Gd) contents are investigated. Experimental results show that when the controlling Gd content is a suitable value(e.g., 13.16%), excellent device performances can be achieved: low interface-state density(6.93 × 10^11 cm^-2·e V-1), small flatband voltage(0.25 V), good capacitance–voltage behavior, small frequency dispersion, and low gate leakage current(2.29× 10^-6 A/cm^2 at Vg = Vfb + 1 V). These could be attributed to the repair of oxygen vacancies, the increase of conduction band offset, and the suppression of germanate and suboxide Ge Ox at/near the high k/Ge interface by doping suitable Gd into Hf ON.

Impact of Native Defects in the High Dielectric Constant Oxide HfSiO_4 on MOS Device Performance

Native dejects in HfSiO4 are investigated by first principles calculations. Transition levels of native detects can be accurately described by employing the nonlocal HSE06 hybrid functional. This methodology overcomes the band gap problem in traditional functionals. By band alignments among the Si, GaAs and HfSiO4. we are able to determine the position of defect levels in Si and GaAs relative to the HfSiO4 band gap. We evaluate the. possibility of these defects acting as fixed charge. Native defects lead to the change of valence and conduction band offsets. Gate leakage current is evaluated by the band offset. In addition, we also investigate diffusions of native defects, and discuss how they affect the MOS device performance.

Improved interface properties of an HfO_2 gate dielectric GaAs MOS device by using SiN_x as an interfacial passivation layer

A GaAs metal-oxide-semiconductor （MOS） capacitor with HfO2 as gate dielectric and silicon nitride （SiNx） as the interlayer （IL） is fabricated. Experimental results show that the sample with the SiNx IL has an improved capacitance- voltage characteristic, lower leakage current density （0.785 × 10^-6 Alcm^2 at Vfo ＋ 1 V） and lower interface-state density （2.9 × 10^12 eV^-1 ·cm^-2） compared with other samples with N2- or NH3-plasma pretreatment. The influences of post- deposition annealing temperature on electrical properties are also investigated for the samples with SiNx IL. The sample annealed at 600 ℃ exhibits better electrical properties than that annealed at 500 ℃, which is attributed to the suppression of native oxides, as confirmed by XPS analyses.

Discussion on the Electron and Hole Effective Masses in Thermal Silicon

This review and research study provides conclusive discussion on the electron and hole effective masses in thermal silicon dioxide placing their values at 0.42m and 0.58m,where m is the free electron mass,correct to two decimal places.Only one of the masses needs to be determined as the electron and hole masses in materials add up to be equal to free electron mass with the hole effective mass being larger than the electron effective mass.The review also convinces the reader that the CBO(conduction band offset)or the Si-SiO2 barrier height at the oxide/silicon interface of a Si MOS(metal-oxide-semiconductor)device is 3.20 eV.

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.

Enhanced electroluminescence from nanocrystallite Si based MOSLED by interfacial Si nanopyramids

The interracial Si nano-pyralnid-enhanced electroluminescence （EL） of an ITO/SiOx/p-Si/Al metal-oxidesemiconductor （MOS） diode with turn-on voltage of 50 V, threshold current of 1.23 mA/cm^2, output power of 16 nW, and lifetime of 10 h is reported.

Low threshold voltage light-emitting diode in silicon-based standard CMOS technology

Low-voltage silicon （Si）-based light-emitting diode （LED） is designed based on the former research of LED in Si-based standard complementary metal oxide semiconductor （CMOS） technology. The low-voltage LED is designed under the research of cross-finger structure LEDs and sophisticated structure enhanced LEDs for high efficiency and stable light source of monolithic chip integration. The device size of low-voltage LED is 45.85x38.4 （#m）, threshold voltage is 2.2 V in common condition, and temperature is 27 ~C. The external quantum efficiency is about 10-6 at stable operating state of 5 V and 177 mA.

Comparison of interfacial and electrical properties between Al_2O_3 and ZnO as interface passivation layer of GaAs MOS device with HfTiO gate dielectric

GaAs metal–oxide–semiconductor（MOS） capacitors with HfTiO as the gate dielectric and Al2O3 or ZnO as the interface passivation layer（IPL） are fabricated. X-ray photoelectron spectroscopy reveals that the Al2O3 IPL is more effective in suppressing the formation of native oxides and As diffusion than the ZnO IPL. Consequently, experimental results show that the device with Al2O3 IPL exhibits better interfacial and electrical properties than the device with ZnO IPL： lower interface-state density（7.2×10^12 eV1cm^2/, lower leakage current density（3.60×10^7A/cm^2 at Vg D1 V） and good C–V behavior.

Mathematical modeling of nanoscale MOS capacitance in the presence of depletion and energy quantization in a poly-silicon gate

A model has been developed to study the effect of depletion and energy quantization at the poly-silicon /oxide interface on the behavior of a nanometer scale n-MOSFET.A model of inversion charge density,including the inversion layer quantization using the variation approach in the substrate,has also been produced.Using the exact calculations of the polygate potential under the depletion and quantization conditions,a C-V model has been developed. All the results have been compared with the numerical models reported in existing literature and they show good agreement.

Optoelectronic devices based on two-dimensional transition metal dichalcogenides

In the past few years, two-dimensional （2D） transition metal dichalcogenide （TMDC） materials have attracted increasing attention of the research community, owing to their unique electronic and optical properties, ranging from the valley-spin coupling to the indirect-to-direct bandgap transition when scaling the materials from multi-layer to monolayer. These properties are appealing for the development of novel electronic and optoelectronic devices with important applications in the broad fields of communication, computation, and healthcare. One of the key features of the TMDC family is the indirect-to-direct bandgap transition that occurs when the material thickness decreases from multilayer to monolayer, which is favorable for many photonic applications. TMDCs have also demonstrated unprecedented flexibility and versatility for constructing a wide range of heterostructures with atomic-level control over their layer thickness that is also free of lattice mismatch issues. As a result, layered TMDCs in combination with other 2D materials have the potential for realizing novel high-performance optoelectronic devices over a broad operating spectral range. In this article, we review the recent progress in the synthesis of 2D TMDCs and optoelectronic devices research. We also discuss the challenges facing the scalable applications of the family of 2D materials and provide our perspective on the opportunities offered by these materials for future generations of nanophotonics technology.

Few-layer MoS2-deposited microfiber as highly nonlinear photonic device for pulse shaping in a fiber laser [Invited]

Two-dimensional（2D） materials have emerged as attractive mediums for fabricating versatile optoelectronic devices. Recently, few-layer molybdenum disulfide（MoS2）, as a shining 2D material, has been discovered to possess both the saturable absorption effect and large nonlinear refractive index. Herein, taking advantage of the unique nonlinear optical properties of MoS2, we fabricated a highly nonlinear saturable absorption photonic device by depositing the few-layer MoS2 onto the microfiber. With the proposed MoS2 photonic device, apart from the conventional soliton patterns, the mode-locked pulses could be shaped into some new soliton patterns, namely,multiple soliton molecules, localized chaotic multipulses, and double-scale soliton clusters. Our findings indicate that the few-layer MoS2-deposited microfiber could operate as a promising highlynonlinear photonic device for the related nonlinear optics applications.

Coexistence of bound soliton and harmonic mode-locking soliton in an ultrafast fiber laser based on MoS2-deposited microfiber photonic device

As the typical material of two-dimensional transition metal dichalcogenides（TMDs）, few-layered MoS2 possesses broadband saturable absorption and a large nonlinear refractive index, which could be regarded as a promising candidate for dual-function photonic device fabrication. In this work, the coexistence of a bound soliton and harmonic mode-locking soliton was demonstrated in an ultrafast fiber laser based on a MoS2-deposited microfiber photonic device. Through a band-pass filter, each multi-soliton state was investigated separately. The bound soliton has periodic spectral modulation of 1.55 nm with a corresponding pulse separation of 5.16 ps.The harmonic mode-locking soliton has the repetition rate of 479 MHz, corresponding to the 65th harmonic of the fundamental repetition rate. The results indicated that there exist more possibilities of different multi-soliton composites, which would enhance our understanding of multi-soliton dynamics.

Novel electrical characterization for advanced CMOS gate dielectrics

This paper reviews the following electrical characterization techniques for measuring the microscopic bonding structures, impurities, and electrically active defects in advanced CMOS gate stacks： 1） inelastic electron tunneling spectroscopy （IETS）, 2） lateral profiling of threshold voltages, interface-trap density, and oxide charge density distributions along the channel of an MOSFET, and 3） pulse agitated substrate hot electron injection （PASHEI） technique for measuring trapping effects in the gate dielectric at low and modest gate voltages.

Enabling novel device functions with black phosphorus/MoS2 van der Waals heterostructures

Van der Waals heterostructure,which consists of various twodimensional(2D)layered materials stacked along the direction perpendicular to their 2D plane,has emerged as a promising material system for device applications in recent years[1].Due to the weak van der Waals interlayer force,2D layered materials with very different lattice constants can be stacked without being constrained by the traditional‘‘lattice-match"condition to form

Sub-nanosecond silicon-on-insulator optical micro-ring switch with low crosstalk

We demonstrate a sub-nanosecond electro-optical switch with low crosstalk in a silicon-on-insulator （SOI） dual-coupled micro-ring embedded with p-i-n diodes. A crosstalk of -23 dB is obtained in the 20-μm-radius micro-ring with the well-designing asymmetric dual-coupling structure. By optimizations of the doping profiles and the fabrication processes, the sub-nanosecond switch-on/off time of 〈400 ps is finally realized under an electrical pre-emphasized driving signal. This compact and fast-response micro-ring switch, which can be fabricated by complementary metal oxide semiconductor （CMOS） compatible technologies, have enormous potential in optical interconnects of multicore networks-on-chip.

Reverse current reduction of Ge photodiodes on Si without post-growth annealing

A new approach to reduce the reverse current of Ge pin photodiodes on Si is presented, in which an i-Si layer is inserted between Ge and top Si layers to reduce the electric field in the Ge layer. Without post- growth annealing, the reverse current density is reduced to -10 mA/cm^2 at -1 V, i.e., over one order of magnitude lower than that of the reference photodiode without i-Si layer. However, the responsivity of the photodiodes is not severely compromised. This lowered-reverse-current is explained by band-pinning at the i-Si/i-Ge interface. Barrier lowering mechanism induced by E-field is also discussed. The presented ＂non-thermal＂ approach to reduce reverse current should accelerate electronics-photonics convergence by using Oe on the Si complementary metal oxide semiconductor （CMOS） platform.

Coarse error analysis and correction of a two-dimensional triangulation range finder

A real-time two-dimensional （2D） triangulation range finder is presented, which is composed of two linear complementary metal oxidation semiconductor （CMOS） chips, two camera lenses, and four light emitting diodes （LEDs）. The high order distortion in image aberrations is the main factor responsible for the coarse errors. The theoretical prediction is in good agreement with experiments and the correction equation is used to obtain more reliable results with the unique distortion coefficient in tile whole working region.