Multivariate rational regression and its application in semiconductor device modeling

Physics equation-based semiconductor device modeling is accurate but time and money consuming.The need for studying new material and devices is increasing so that there has to be an efficient and accurate device modeling method. In this paper, two methods based on multivariate rational regression（MRR） for device modeling are proposed. They are single-pole MRR and double-pole MRR. The two MRR methods are proved to be powerful in nonlinear curve fitting and have good numerical stability. Two methods are compared with OLS and LASSO by fitting the SMIC 40 nm MOS-FET I–V characteristic curve and the normalized mean square error of Single-pole MRR is 3.02 × 10^-8 which is 4 magnitudes less than an ordinary least square. The I–V characteristics of CNT-FET and performance indicators（noise factor, gain, power） of a low noise amplifier are also modeled by using MRR methods. The results show MRR methods are very powerful methods for semiconductor device modeling and have a strong nonlinear curve fitting ability.

Use of sensory substitution devices as a model system for investigating cross-modal neuroplasticity in humans

Blindness provides an unparalleled opportunity to study plasticity of the nervous system in humans.Seminal work in this area examined the often dramatic modifications to the visual cortex that result when visual input is completely absent from birth or very early in life（Kupers and Ptito,2014）.More recent studies explored what happens to the visual pathways in the context of acquired blindness.This is particularly relevant as the majority of diseases that cause vision loss occur in the elderly.

A novel physical parameter extraction approach for Schottky diodes

Parameter extraction is an important step for circuit simulation methods that are based on physical models of semiconductor devices. A novel physical parameter extraction approach for Schottky diodes is proposed in this paper. By employing a set of analytical formulas, this approach extracts all of the necessary physical parameters of the diode chip in a unique way. It then extracts the package parasitic parameters with a curve-fitting method. To validate the proposed approach, a model HSMS-282 c commercial Schottky diode is taken as an example. Its physical parameters are extracted and used to simulate the diode＇s electrical characteristics. The simulated results based on the extracted parameters are compared with the measurements and a good agreement is obtained, which verifies the feasibility and accuracy of the proposed approach.

Comprehensive Analysis of CuIn_1-xGa_xSe₂Based Solar Cells with Zn_1-yMg_yO Buffer Layer

The development of cadmium-free CIGS solar cells with high conversion efficiency is crucial due to the toxicity of cadmium. Zinc-based buffer layers seem to be the most promising. In this paper, a numerical analysis using SCAPS-1D software was used to explore the Zn(Mg,O) layer as an alternative to the toxic CdS layer. The effect of several properties such as thickness, doping, Mg concentration of the Zn(Mg,O) layer on the current-voltage parameters was explored and their optimal values were proposed. The simulation results reveal that the optimal value of the ZMO layer thickness is approximately 40 nm, the doping at 1017 cm-3 and an Mg composition between 0.15 and 0.2. In addition, the effect of Gallium (Ga) content in the absorber as well as the Zn(Mg,O)/CIGS interface properties on the solar cell’s performance was examined. The results show that contrary to the CdS buffer layer, the best electrical characteristics of the ZMO/CIGS heterojunction are obtained using a Ga-content equal to 0.4 and high interface defect density or unfavorable band alignment may be the causes of poor performances of Zn(Mg,O)/CIGS solar cells in the case of low and high Mg-contents.

Design and Modelling of Piezoelectric Road Energy Harvesting

In recent years, road piezoelectric energy harvesting (RPEH) has attracted great attention from industry and academia, as it can provide power to traffic ancillary facilities and low-power wireless sensor devices to support car networking and intelligent transportation. The output power of RPEH in a recent research project demonstrated a watt level RPEH. In this proposal, we propose to harvest energy from piezoelectric modules (also called stacks) to power selected highways, tolls, and bridges in Pennsylvania. The project incorporates electrical, mechanical, and civil engineering works. The proposed smart highway RPEH will be conducted using optimization parameters to evaluate the system performance and trade-offs. MATLAB will be used with other optimization solvers in problem modeling and optimization. During this project, an RPEH hardware system will be constructed. The system will include a piezoelectric module, rectifier (AC-DC), Storage battery, data acquisition system (DAQ), and computer. The captured data will be analyzed using MATLAB/Simulink. The results show that optimum harvested parameters were addressed when the thickness is selected as 2 mm.

Energy level engineering of charge selective contact and halide perovskite by modulating band offset:Mechanistic insights

Mixed cation and anion based perovskites solar cells exhibited enhanced stability under outdoor conditions,however,it yielded limited power conversion efficiency when TiO_(2) and Spiro-OMeTAD were employed as electron and hole transport layer(ETL/HTL)respectively.The inevitable interfacial recombination of charge carriers at ETL/perovskite and perovskite/HTL interface diminished the efficiency in planar(n-i-p)perovskite solar cells.By employing computational approach for uni-dimensional device simulator,the effect of band offset on charge recombination at both interfaces was investigated.We noted that it acquired cliff structure when the conduction band minimum of the ETL was lower than that of the perovskite,and thus maximized interfacial recombination.However,if the conduction band minimum of ETL is higher than perovskite,a spike structure is formed,which improve the performance of solar cell.An optimum value of conduction band offset allows to reach performance of 25.21%,with an open circuit voltage(VOC)of 1231 mV,a current density JSC of 24.57 mA/cm^(2) and a fill factor of 83.28%.Additionally,we found that beyond the optimum offset value,large spike structure could decrease the performance.With an optimized energy level of Spiro-OMeTAD and the thickness of mixed-perovskite layer performance of 26.56% can be attained.Our results demonstrate a detailed understanding about the energy level tuning between the charge selective layers and perovskite and how the improvement in PV performance can be achieved by adjusting the energy level offset.

Spinal fixation after laminectomy in pigs prevents postoperative spinal cord injury

Background:A safe,effective,and ethically sound animal model is essential for preclinical research to investigate spinal medical devices.We report the initial failure of a porcine spinal survival model and a potential solution by fixating the spine.Methods:Eleven female Dutch Landrace pigs underwent a spinal lumbar interlaminar decompression with durotomy and were randomized for implantation of a medical device or control group.Magnetic resonance imaging(MRI)was performed before termination.Results:Neurological deficits were observed in 6 out of the first 8 animals.Three of these animals were terminated prematurely because they reached the predefined humane endpoint.Spinal cord compression and myelopathy was observed on postoperative MRI imaging.We hypothesized postoperative spinal instability with epidural hematoma,inherent to the biology of the model,and subsequent spinal cord injury as a potential cause.In the subsequent 3 animals,we fixated the spine with Lubra plates.All these animals recovered without neurological deficits.The extent of spinal cord compression on MRI was variable across animals and did not seem to correspond well with neurological outcome.Conclusion:This study shows that in a porcine in vivo model of interlaminar decompression and durotomy,fixation of the spine after lumbar interlaminar decompression is feasible and may improve neurological outcomes.Additional research is necessary to evaluate this hypothesis.

Experimental and Simulation Validation of Piezoelectric Road Energy Harvesting

This project strived to develop a prototype road piezoelectric energy harvester RPEH system using five Lead Zirconate Titanate (PZT) PZT 5H modules (stacks) that are embedded in the road by means of a housing unit to harvest energy from vehicles stressing the modules. The work is an extension of our previous published work in the same journal. The design considered many factors to optimize the harvested energy. The proposed system first captures mechanical energy using a designed module that transfers the energy to the piezoelectric stacks. Then the captured energy will be converted into electrical energy by the piezoelectric phenomenon. The harvested energy is stored in a storage device, then analyzed by an oscilloscope through the acquisition of the harvested voltage, current, power, and energy. When testing the RPEH with the wheel tracking machine, varying resistor loads where connected to the output of the RPEH to address the optimum power delivered to the load. The optimum load was found to be 950 kΩ, and the optimal harvested energy was recorded as 45 uJ.

Modeling and simulation of nanoscale tri-gate MOSFETs including quantum effects

Quantum effects are predominant in tri-gate MOSFETs, so a model should be developed. For the first time, this paper presents the analytical model for quantization effects of thin film silicon tri-gate MOSFETs by using variational approach. An analytical expression of the inversion charge distribution function（ICDF） or wave function for the tri-gate MOSFETs has been obtained. This obtained ICDF is used to calculate the important device parameters, such as the inversion charge centroid and inversion charge density. The results are validated against with the simulation data.

Dynamic infrared scene simulation using grayscale modulation of digital micro-mirror device

Dynamic infrared scene simulation is for discovering and solving the problems encountered in designing, developing and manufacturing infrared imaging guidance weapons. The infrared scene simulation is explored by using the digital grayscale modulation method. The infrared image modulation model of a digital micro-mirror device （DMD） is established and then the infrared scene simulator prototype which is based on DMD grayscale modulation is developed. To evaluate its main parameters such as resolution, contrast, minimum temperature difference, gray scale, various DMD subsystems such as signal decoding, image normalization, synchronization drive, pulse width modulation （PWM） and DMD chips are designed. The infrared scene simulator is tested on a certain infrared missile seeker. The test results show preliminarily that the infrared scene simulator has high gray scale, small geometrical distortion and highly resolvable imaging resolution and contrast and yields high-fidelity images, thus being able to meet the requirements for the infrared scene simulation inside a laboratory.

A Cryogenic 10-bit Successive Approximation Register Analog-to-Digital Converter Design with Modified Device Model

A 10-bit 500 kHz low-power successive approximation register(SAR)analog-to-digital converter(ADC)for cryogenic infrared readout circuit is proposed.To improve the simulation accuracy of metal-oxidesemiconductor field-efect transistors(MOSFETs),corresponding modification in device model is presented on the basis of BSIM3v3 with parameter extraction at 77 K.Corresponding timing is adopted in comparator to eliminate the influence caused by abnormal performance of MOSFETs at 77 K.The SAR ADC is fabricated and verified by standard 0.35μm complementary metal oxide semiconductor(CMOS)process.At 77 K,measurement results show that signal to noise and distortion ratio(SNDR)is 54.74 dB and efective number of bits(ENOB)is 8.8 at the sampling rate of 500 kHz.The total circuit consumes 0.6 mW at 3.3 V power supply.

Optimization of ohmic contact for InP-based transferred electronic devices

The effect of the annealing time and annealing temperature on Ni/Ge/Au electrode contacts deposited on the n-type InP contact layer has been studied using a circular transmission line model. The minimum specific contact resistance of 3.210 7 cm2was achieved on the low-doped n-type InP contact layer with a 40 s anneal at 425 ℃. In order to improve the ohmic contact and reduce the difficulty in the fabrication of the high doped InP epi-layer, the doping concentration in the InP contact layer was chosen to be 51018cm 3in the fabrication of transferred electronic devices. Excellent differential negative resistance properties were obtained by an electron beam evaporating the Ni/Ge/Au/Ge/Ni/Au composite electrode on an InP epi-layer with a 60 s anneal at 380 ℃.

Effects of defect states on the performance of perovskite solar cells

We built an ideal perovskite solar cell model and investigated the effects of defect states on the so- lar cell＇s performance. The verities of defect states with a different energy level in the band gap and those in the absorption layer CH3NH3PbI3 （MAPbI3）, the interface between the buffer layer/MAPbI3, and the interface be- tween the hole transport material （HTM） and MAPbI3, were studied. We have quantitatively analyzed these effects on perovskite solar cells＇ performance parameters. They are open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency. We found that the performances of perovskite solar cells change worse with defect state density increasing, but when defect state density is lower than 1016 cm^-3, the effects are small. Defect states in the absorption layer have much larger effects than those in the adjacent interface layers. The per-ovskite solar cells have better performance as its working temperature is reduced. When the thickness of MAPbI3 is about 0.3μm, perovskite solar cells show better comprehensive performance, while the thickness 0.05μm for Spiro-OMeTAD is enough.

Estimation of the optical loss in bent-waveguide superluminescent diodes by an analytical method

The optical loss in the bent region is one of the key features for bent-waveguide superluminescent diodes that affects the device performance greatly under some conditions. For the purpose of device fabrication and optimization, it will be helpful if this bend loss can be estimated. In this letter, we have derived an analytical formula which can be used to get the bend-loss coefficient by fitting the P-I curves of the devices. It is proved that the formula is successful in estimating the loss coefficients from the P-I curves simulated from a complicated quantum-dot device model. We expect this method could also be valid in estimating bend losses of actual devices.

Effects of defect states on the performance of CuInGaSe_2 solar cells

Device modeling has been carried out to investigate the effects of defect states on the performance of ideal CulnGaSe2 （CIGS） thin film solar cells theoretically. The varieties of defect states （location in the band gap and densities） in absorption layer CIGS and in buffer layer CdS were examined. The performance parameters： open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency for different defect states were quantitatively analyzed. We found that defect states always harm the performance of CIGS solar cells, but when defect state density is less than 10 14 cm-3 in CIGS or less than 10 18 cm-3 in CdS, defect states have little effect on the performances. When defect states are located in the middle of the band gap, they are more harmful. The effects of temperature and thickness are also considered. We found that CIGS solar cells have optimal performance at about 170 K and 2 μm of CIGS is enough for solar light absorption.

Compact model for ballistic single wall CNTFET under quantum capacitance limit

This paper proposes a compact model for carbon nanotube field effect transistor（CNTFET） based on surface potential and conduction band minima. The proposed model relates the I–V characteristics to chirality under quantum capacitance limit. C–V characteristics have been efficiently modelled for different capacitance models which are used to find the relationship between CNT surface potential and gate voltage. The role of different capacitances is discussed and it has been found that the proposed circuit compact model strictly follows quantum capacitance limit. The proposed model is efficiently designed for circuit simulations as it denies self-consistent numerical simulation. Furthermore, this compact model is compared with experimental results. The model has been used to simulate an inverter using HSPICE.

Adaptive suppression of passive intermodulation in digital satellite transceivers

For the performance issues of satellite transceivers suffering passive intermodulation interference,a novel and effective digital suppression algorithm is presented in this paper.In contrast to analog approaches,digital passive intermodulation（PIM） suppression approaches can be easily reconfigured and therefore are highly attractive for future satellite communication systems.A simplified model of nonlinear distortion from passive microwave devices is established in consideration of the memory effect.The multiple high-order PIM products falling into the receiving band can be described as a bilinear predictor function.A suppression algorithm based on a bilinear polynomial decorrelated adaptive filter is proposed for baseband digital signal processing.In consideration of the time-varying characteristics of passive intermodulation,this algorithm can achieve the rapidness of online interference estimation and low complexity with less consumption of resources.Numerical simulation results show that the algorithm can effectively compensate the passive intermodulation interference,and achieve a high signal-to-interference ratio gain.