Theory of steady‐state high‐field hole transport in GaSb and AlxGa1−xSb: The impact ionization resonance

1985 ◽  
Vol 57 (6) ◽  
pp. 1971-1977 ◽  
Author(s):  
Kevin Brennan ◽  
Karl Hess ◽  
Yia‐Chung Chang
Keyword(s):  
Steady State ◽  
High Field ◽  
Impact Ionization ◽  
Hole Transport ◽  
The Impact

IMPACT IONIZATION AND HIGH FIELD EFFECTS IN WIDE BAND GAP SEMICONDUCTORS

2001 ◽  
Vol 11 (02) ◽  
pp. 511-524 ◽  
Author(s):  
M. REIGROTZKI ◽  
J. R. MADUREIRA ◽  
A. KULIGK ◽  
N. FITZER ◽  
R. REDMER ◽  
...  
Keyword(s):  
Electric Fields ◽  
High Field ◽  
Impact Ionization ◽  
Electron Distribution Function ◽  
Wide Band ◽  
Ionization Rate ◽  
Wide Bandgap ◽  
Bandgap Semiconductors ◽  
Impact Ionization Rate ◽  
The Impact

Impact ionization plays a crucial role for electron transport in wide-bandgap semiconductors at high electric fields. Therefore, a realistic band structure has to be used in calculations of the microscopic scattering rate, as well as high field quantum corrections such as the intercollisional field effect. Here we consider both, and evaluate the impact ionization rate for wide-bandgap materials such as ZnS. A pronounced softening of the impact ionization threshold is obtained, as found earlier for materials like Si and GaAs. This field dependent impact ionization rate is included within a full-band ensemble Monte Carlo simulation of high field transport in ZnS. Although the impact ionization rate itself is strongly affected, little effect is observed on measurable quantities such as the impact ionization coefficient or the electron distribution function itself.

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

scholarly journals Engineered tunneling layer with enhanced impact ionization for detection improvement in graphene/silicon heterojunction photodetectors

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jun Yin ◽  
Lian Liu ◽  
Yashu Zang ◽  
Anni Ying ◽  
Wenjie Hui ◽  
...  
Keyword(s):  
High Performance ◽  
Impact Ionization ◽  
Low Cost ◽  
Atomic Layer ◽  
Light Illumination ◽  
Insulation Material ◽  
Defect States ◽  
Uv Illumination ◽  
Layer Deposition ◽  
The Impact

AbstractHere, an engineered tunneling layer enhanced photocurrent multiplication through the impact ionization effect was proposed and experimentally demonstrated on the graphene/silicon heterojunction photodetectors. With considering the suitable band structure of the insulation material and their special defect states, an atomic layer deposition (ALD) prepared wide-bandgap insulating (WBI) layer of AlN was introduced into the interface of graphene/silicon heterojunction. The promoted tunneling process from this designed structure demonstrated that can effectively help the impact ionization with photogain not only for the regular minority carriers from silicon, but also for the novel hot carries from graphene. As a result, significantly enhanced photocurrent as well as simultaneously decreased dark current about one order were accomplished in this graphene/insulation/silicon (GIS) heterojunction devices with the optimized AlN thickness of ~15 nm compared to the conventional graphene/silicon (GS) devices. Specifically, at the reverse bias of −10 V, a 3.96-A W−1 responsivity with the photogain of ~5.8 for the peak response under 850-nm light illumination, and a 1.03-A W−1 responsivity with ∼3.5 photogain under the 365 nm ultraviolet (UV) illumination were realized, which are even remarkably higher than those in GIS devices with either Al2O3 or the commonly employed SiO2 insulation layers. This work demonstrates a universal strategy to fabricate broadband, low-cost and high-performance photo-detecting devices towards the graphene-silicon optoelectronic integration.

scholarly journals Device Modeling and Design of Inverted Solar Cell Based on Comparative Experimental Analysis between Effect of Organic and Inorganic Hole Transport Layer on Morphology and Photo-Physical Property of Perovskite Thin Film

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2191
Author(s):  
Xiaolan Wang ◽  
Xiaoping Zou ◽  
Jialin Zhu ◽  
Chunqian Zhang ◽  
Jin Cheng ◽  
...  
Keyword(s):  
Light Absorption ◽  
Short Circuit ◽  
Perovskite Solar Cells ◽  
Open Circuit ◽  
Hole Transport ◽  
Transport Layer ◽  
Hole Transport Layer ◽  
Functional Layer ◽  
Perovskite Layer ◽  
The Impact

It is crucial to find a good material as a hole transport layer (HTL) to improve the performance of perovskite solar cells (PSCs), devices with an inverted structure. Polyethylene dioxythiophene-poly (styrene sulfonate) (PEDOT:PSS) and inorganic nickel oxide (NiOx) have become hotspots in the study of hole transport materials in PSCs on account of their excellent properties. In our research, NiOx and PEDOT: PSS, two kinds of hole transport materials, were prepared and compared to study the impact of the bottom layer on the light absorption and morphology of perovskite layer. By the way, some experimental parameters are simulated by wx Analysis of Microelectronic and Photonic Structures (wxAMPS). In addition, thin interfacial layers with deep capture levels and high capture cross sections were inserted to simulate the degradation of the interface between light absorption layer and PEDOT:PSS. This work realizes the combination of experiment and simulation. Exploring the mechanism of the influence of functional layer parameters plays a vital part in the performance of devices by establishing the system design. It can be found that the perovskite film growing on NiOx has a stronger light absorption capacity, which makes the best open-circuit voltage of 0.98 V, short-circuit current density of 24.55 mA/cm2, and power conversion efficiency of 20.01%.

Temperature Dependence of Hole Impact Ionization Coefficient in 4H-SiC Photodiodes

2009 ◽  
Vol 615-617 ◽  
pp. 311-314 ◽  
Author(s):  
W.S. Loh ◽  
J.P.R. David ◽  
B.K. Ng ◽  
Stanislav I. Soloviev ◽  
Peter M. Sandvik ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Impact Ionization ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Different Temperatures ◽  
Ionization Coefficients ◽  
Increasing Temperature ◽  
The Impact ◽  
Good Agreement ◽  
Ionization Rates

Hole initiated multiplication characteristics of 4H-SiC Separate Absorption and Multiplication Avalanche Photodiodes (SAM-APDs) with a n- multiplication layer of 2.7 µm were obtained using 325nm excitation at temperatures ranging from 300 to 450K. The breakdown voltages increased by 200mV/K over the investigated temperature range, which indicates a positive temperature coefficient. Local ionization coefficients, including the extracted temperature dependencies, were derived in the form of the Chynoweth expression and were used to predict the hole multiplication characteristics at different temperatures. Good agreement was obtained between the measured and the modeled multiplication using these ionization coefficients. The impact ionization coefficients decreased with increasing temperature, corresponding to an increase in breakdown voltage. This result agrees well with the multiplication characteristics and can be attributed to phonon scattering enhanced carrier cooling which has suppressed the ionization process at high temperatures. Hence, a much higher electric field is required to achieve the same ionization rates.

Measurement of the impact ionization rates in Al0.06Ga0.94Sb

1990 ◽  
Vol 57 (3) ◽  
pp. 249-251 ◽  
Author(s):  
H. Kuwatsuka ◽  
T. Mikawa ◽  
S. Miura ◽  
N. Yasuoka ◽  
Y. Kito ◽  
...  
Keyword(s):  
Impact Ionization ◽  
The Impact ◽  
Ionization Rates

scholarly journals Research on Cooperative Innovation Behavior of Industrial Cluster Based on Subject Adaptability

2016 ◽  
Vol 2016 ◽  
pp. 1-19 ◽  
Author(s):  
Xiaohui Jia ◽  
Minghui Jiang ◽  
Lei Shi
Keyword(s):  
Steady State ◽  
Evolutionary Game ◽  
Industrial Cluster ◽  
Industrial Clusters ◽  
Government Support ◽  
Correlated Equilibrium ◽  
Game Model ◽  
Cooperative Innovation ◽  
The Cost ◽  
The Impact

From the perspective of the interactive cooperation among subjects, this paper portrays the process of cooperative innovation in industrial cluster, in order to capture the correlated equilibrium relationship among them. Through the utilization of two key tools, evolutionary stable strategy and replicator dynamics equations, this paper considers the cost and gains of cooperative innovation and the amount of government support as well as other factors to build and analyze a classic evolutionary game model. On this basis, the subject’s own adaptability is introduced, which is regarded as the system noise in the stochastic evolutionary game model so as to analyze the impact of adaptability on the game strategy selection. The results show that, in the first place, without considering subjects’ adaptability, their cooperation in industrial clusters depends on the cost and gains of innovative cooperation, the amount of government support, and some conditions that can promote cooperation, namely, game steady state. In the second place after the introduction of subjects’ adaptability, it will affect both game theory selection process and time, which means that the process becomes more complex, presents the nonlinear characteristics, and helps them to make faster decisions in their favor, but the final steady state remains unchanged.

Life Prediction of Power Turbine Components for High Exhaust Back Pressure Applications: Part I — Disks

2015 ◽  
Author(s):  
Dipankar Dua ◽  
Brahmaji Vasantharao
Keyword(s):  
Steady State ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Life Prediction ◽  
Creep Damage ◽  
Back Pressure ◽  
System Level ◽  
Cyclic Life ◽  
Power Turbine ◽  
The Impact

Industrial and aeroderivative gas turbines when used in CHP and CCPP applications typically experience an increased exhaust back pressure due to pressure losses from the downstream balance-of-plant systems. This increased back pressure on the power turbine results not only in decreased thermodynamic performance but also changes power turbine secondary flow characteristics thus impacting lives of rotating and stationary components of the power turbine. This Paper discusses the Impact to Fatigue and Creep life of free power turbine disks subjected to high back pressure applications using Siemens Energy approach. Steady State and Transient stress fields have been calculated using finite element method. New Lifing Correlation [1] Criteria has been used to estimate Predicted Safe Cyclic Life (PSCL) of the disks. Walker Strain Initiation model [1] is utilized to predict cycles to crack initiation and a fracture mechanics based approach is used to estimate propagation life. Hyperbolic Tangent Model [2] has been used to estimate creep damage of the disks. Steady state and transient temperature fields in the disks are highly dependent on the secondary air flows and cavity dynamics thus directly impacting the Predicted Safe Cyclic Life and Overall Creep Damage. A System-level power turbine secondary flow analyses was carried out with and without high back pressure. In addition, numerical simulations were performed to understand the cavity flow dynamics. These results have been used to perform a sensitivity study on disk temperature distribution and understand the impact of various back pressure levels on turbine disk lives. The Steady Sate and Transient Thermal predictions were validated using full-scale engine test and have been found to correlate well with the test results. The Life Prediction Study shows that the impact on PSCL and Overall Creep damage for high back pressure applications meets the product design standards.

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