scholarly journals Boundary Condition for the Modeling of Open-circuited Devices in Non-equilibrium

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 567-572
Author(s):  
Joseph W. Parks ◽  
Kevin F. Brennan
Keyword(s):  
Boundary Condition ◽  
Impact Ionization ◽  
Background Radiation ◽  
Imaging System ◽  
Surface Recombination ◽  
Avalanche Photodiode ◽  
Load Resistance ◽  
Surface Recombination Velocity ◽  
External Current ◽  
The Impact

A boundary condition specifically designed to model open-circuited devices in a macroscopic device simulator is introduced. Other simulation techniques have relied on an external circuit model to regulate the current flow out of a contact thus allowing the potential to remain the controlled variable at the boundary. The limitations of these methods become apparent when modeling open-circuited devices with an exceptionally small or zero output current. In this case, using a standard ohmic-type Dirichlet boundary condition would not yield satisfactory results and attaching the device to an arbitrarily large load resistance is physically and numerically unacceptable. This proposed condition is a true current controlled boundary where the external current is the specified parameter rather than the potential. Using this model, the external current is disseminated into electron and hole components relative to their respective concentration densities at the contact. This model also allows for the inclusion of trapped interface charge and a finite surface recombination velocity at the contact. An example of the use of this boundary condition is performed by modeling a silicon avalanche photodiode operating in the flux integrating mode for use in an imaging system. In this example, the device is biased in steady-state to just below the breakdown voltage and then open-circuited. The recovery of the isolated photodiode back to its equilibrium condition is then determined by the generation lifetime of the material, the quantity of signal and background radiation incident upon the device, and the impact ionization rates.

Optimization of the Specific On-Resistance of 4H-SiC BJTs

2006 ◽  
Vol 527-529 ◽  
pp. 1429-1432 ◽  
Author(s):  
S. Balachandran ◽  
T. Paul Chow ◽  
Anant K. Agarwal
Keyword(s):  
High Voltage ◽  
Minority Carrier ◽  
Surface Recombination ◽  
Surface Recombination Velocity ◽  
Bipolar Junction Transistors ◽  
Carrier Lifetimes ◽  
Minority Carrier Lifetimes ◽  
Recombination Velocity ◽  
The Impact

We evaluate the performance capabilities and limitations of high voltage 4H-SiC based Bipolar Junction Transistors (BJTs). Experimental forward characteristics of a 4kV BJT are studied and simulations are employed to determine the factors behind the higher than expected specific onresistance (Ron,sp) for the device. The impact of material (minority carrier lifetimes), processing (surface recombination velocity) and design (p contact spacing from the emitter mesa) parameters on the forward active performance of this device are discussed and ways to lower Ron,sp, below the unipolar level, and increase the gain (β) are examined.

Forward Active and Blocking Performance of 4H-SiC Bipolar Junction Transistors

2005 ◽  
Vol 888 ◽  
Author(s):  
Santhosh Balachandran ◽  
T. Paul Chow ◽  
Anant Agarwal
Keyword(s):  
High Voltage ◽  
Minority Carrier ◽  
Surface Recombination ◽  
Current Gain ◽  
Surface Recombination Velocity ◽  
Bipolar Junction Transistors ◽  
Carrier Lifetimes ◽  
Minority Carrier Lifetimes ◽  
Recombination Velocity ◽  
The Impact

ABSTRACTWe evaluate the performance capabilities and limitations of high voltage 4H-SiC based Bipolar Junction Transistors (BJTs). Experimental forward characteristics of a 4kV BJT are studied and simulations are employed to determine the factors behind the higher than expected specific on-resistance (Ron,sp) for the device. The impact of material (minority carrier lifetimes), processing (surface recombination velocity) and design (p contact spacing from the emitter mesa) parameters on the forward active performance of this device are discussed and ways to lower Ron,sp, below the unipolar level, and increase the gain (β) are examined. A correlation between the open base blocking behavior (forward blocking) and the current gain (forward active) for 4H-SiC based high-voltage BJTs with lightly doped collector regions is presented and experimental device characteristics are utilized to verify our numerical analysis.

A Novel Structure of a-SiN:H/a-Si:H Multilayer Avalanche Photodiode (MAPD)

1993 ◽  
Vol 297 ◽  
Author(s):  
Jiao Lihong ◽  
Meng Zhiguo ◽  
Sun Zhonglin
Keyword(s):  
Reverse Bias ◽  
Impact Ionization ◽  
Incident Light ◽  
Avalanche Photodiode ◽  
Low Noise ◽  
Excess Noise ◽  
Novel Structure ◽  
Ito Glass ◽  
Noise Factors ◽  
The Impact

Because of the lower density of interface states in a-Si:H/a-SiN:H than that in a-Si:H/a-SiC:H, an a-Si:H/a-SiN multilayer reach-through avalanche photodiode is fabricated on an ITO/glass substrate by plasma-enhanced chemical vapor deposition (PECVD) . In order to improve the performance of the a-Si:H/a-SiN:H APD'S, a novel structure is used. By controlling the deposition ratio of silicon and nitrogen of amorphous SiN,the valence band top of a-Si:H is deeper than that of a-SiN:H, that is, the a-Si :H/a-SiN: H system has the electron potential well in a-Si:H, while the hole well is in a-SiN:H, thus we can successfully suppress the hole impact ionization, correspondingly enhance the electron impact ionization effectively.The measurement of current versus voltage is employed to study the multiplication factors and the impact ionization coefficients. The characteristics of a-Si:H/a-SiN:H APD's,such as I-V curves, optical gains, impact ionization rates, excess noise factors, the relative response and the relationship between the breakdown voltage and wavelength, are studied. The electron multiplication factor is Mc=4.5 at reverse bias V=12v. An optical gain of 3.7 at reverse bias VR=12v and an incident light power Pin=3μw is obtained. Homo junction a-Si:H reach-through APD's and homojunction a-Si:H APD's are also fabricated for comparison.The results show that the novel a-Si:H/a-SiN:H APD's is promising in high-gain, low-noise photodetectors.

Analysis of Contaminated Oxide-Silicon Interfaces

2011 ◽  
Vol 178-179 ◽  
pp. 243-248
Author(s):  
Maria Luisa Polignano ◽  
Davide Codegoni ◽  
Luca Castellano ◽  
Stefano Greco ◽  
Gabriella Borionetti ◽  
...  
Keyword(s):  
Surface Segregation ◽  
Surface Recombination ◽  
Interface State ◽  
State Density ◽  
Surface Recombination Velocity ◽  
Organic Contamination ◽  
Conductance Method ◽  
The Impact ◽  
Silicon Interface ◽  
Dlts Spectra

Methods for the analysis of the oxide-silicon interface were compared for their ability to reveal metal segregation at the interface and organic contamination. The impact of these contaminations on surface recombination velocity measurements, on capacitance vs. voltage, conductance vs. voltage and capacitance vs. time measurements and on MOS-DLTS spectra was studied. Niobium-contaminated wafers were used as an example of metal surface segregation, because it was previously shown that niobium is prone to surface segregation. Interface state density measurements obtained by the conductance method showed a limited impact of niobium implantation. Vice versa significant effects were found in MOS-DLTS spectra. For what concerns organic contamination, MOS-DLTS showed the most significant effects from the point-of-view of the intrinsic properties of the silicon oxide - silicon interface, and GOI tests demonstrate a clear impact of the organic contamination on MOS capacitors oxide breakdown events.

scholarly journals Characterization of Impact Ionization Coefficient of ZnO Based on a p-Si/i-ZnO/n-AZO Avalanche Photodiode

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 740
Author(s):  
Gaoming Li ◽  
Xiaolong Zhao ◽  
Xiangwei Jia ◽  
Shuangqing Li ◽  
Yongning He
Keyword(s):  
High Performance ◽  
Impact Ionization ◽  
Single Photon ◽  
Wide Band ◽  
Avalanche Photodiode ◽  
Excess Noise ◽  
Single Photon Detection ◽  
Avalanche Gain ◽  
Ionization Coefficients ◽  
The Impact

The avalanche photodiode is a highly sensitive photon detector with wide applications in optical communication and single photon detection. ZnO is a promising wide band gap material to realize a UV avalanche photodiode (APD). However, the lack of p-type doping, the strong self-compensation effect, and the scarcity of data on the ionization coefficients restrain the development and application of ZnO APD. Furthermore, ZnO APD has been seldom reported before. In this work, we employed a p-Si/i-ZnO/n-AZO structure to successfully realize electron avalanche multiplication. Based on this structure, we investigated the band structure, field profile, Current–Voltage (I-V) characteristics, and avalanche gain. To examine the influence of the width of the i-ZnO layer on the performance, we changed the i-ZnO layer thickness to 250, 500, and 750 nm. The measured breakdown voltages agree well with the corresponding threshold electric field strengths that we calculated. The agreement between the experimental data and calculated results supports our analysis. Finally, we provide data on the impact ionization coefficients of electrons for ZnO along the (001) direction, which is of great significance in designing high-performance low excess noise ZnO APD. Our work lays a foundation to realize a high-performance ZnO-based avalanche device.

Surface recombination effects on minority carrier diffusion length measurements using electron beam-induced current

1990 ◽  
Vol 48 (4) ◽  
pp. 744-745
Author(s):  
D.P. Malta ◽  
M.L. Timmons
Keyword(s):  
Electron Beam ◽  
Beam Energy ◽  
Minority Carrier ◽  
Diffusion Length ◽  
Effective Diffusion ◽  
Surface Recombination ◽  
Surface Recombination Velocity ◽  
Logarithmic Scale ◽  
Minority Carrier Diffusion Length ◽  
Carrier Diffusion

Measurement of the minority carrier diffusion length (L) can be performed by measurement of the rate of decay of excess minority carriers with the distance (x) of an electron beam excitation source from a p-n junction or Schottky barrier junction perpendicular to the surface in an SEM. In an ideal case, the decay is exponential according to the equation, I = Ioexp(−x/L), where I is the current measured at x and Io is the maximum current measured at x=0. L can be obtained from the slope of the straight line when plotted on a semi-logarithmic scale. In reality, carriers recombine not only in the bulk but at the surface as well. The result is a non-exponential decay or a sublinear semi-logarithmic plot. The effective diffusion length (Leff) measured is shorter than the actual value. Some improvement in accuracy can be obtained by increasing the beam-energy, thereby increasing the penetration depth and reducing the percentage of carriers reaching the surface. For materials known to have a high surface recombination velocity s (cm/sec) such as GaAs and its alloys, increasing the beam energy is insufficient. Furthermore, one may find an upper limit on beam energy as the diameter of the signal generation volume approaches the device dimensions.

scholarly journals Numerical Simulation Analysis of Ag Crystallite Effects on Interface of Front Metal and Silicon in the PERC Solar Cell

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 592
Author(s):  
Myeong Sang Jeong ◽  
Yonghwan Lee ◽  
Ka-Hyun Kim ◽  
Sungjin Choi ◽  
Min Gu Kang ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
High Efficiency ◽  
Open Circuit Voltage ◽  
Surface Recombination ◽  
Open Circuit ◽  
Surface Recombination Velocity ◽  
Metal Interface ◽  
Ag Crystallites ◽  
Recombination Velocity

In the fabrication of crystalline silicon solar cells, the contact properties between the front metal electrode and silicon are one of the most important parameters for achieving high-efficiency, as it is an integral element in the formation of solar cell electrodes. This entails an increase in the surface recombination velocity and a drop in the open-circuit voltage of the solar cell; hence, controlling the recombination velocity at the metal-silicon interface becomes a critical factor in the process. In this study, the distribution of Ag crystallites formed on the silicon-metal interface, the surface recombination velocity in the silicon-metal interface and the resulting changes in the performance of the Passivated Emitter and Rear Contact (PERC) solar cells were analyzed by controlling the firing temperature. The Ag crystallite distribution gradually increased corresponding to a firing temperature increase from 850 ∘C to 950 ∘C. The surface recombination velocity at the silicon-metal interface increased from 353 to 599 cm/s and the open-circuit voltage of the PERC solar cell decreased from 659.7 to 647 mV. Technology Computer-Aided Design (TCAD) simulation was used for detailed analysis on the effect of the surface recombination velocity at the silicon-metal interface on the PERC solar cell performance. Simulations showed that the increase in the distribution of Ag crystallites and surface recombination velocity at the silicon-metal interface played an important role in the decrease of open-circuit voltage of the PERC solar cell at temperatures of 850–900 ∘C, whereas the damage caused by the emitter over fire was determined as the main cause of the voltage drop at 950 ∘C. These results are expected to serve as a steppingstone for further research on improvement in the silicon-metal interface properties of silicon-based solar cells and investigation on high-efficiency solar cells.

scholarly journals Modeling and image quality enhancement for dynamic compressive imaging system

2021 ◽  
Vol 15 ◽  
pp. 174830262110080
Author(s):  
Changjun Zha* ◽  
Qian Zhang* ◽  
Huimin Duan
Keyword(s):  
Image Quality ◽  
Imaging System ◽  
Quality Enhancement ◽  
Target Image ◽  
Compressive Imaging ◽  
Image Quality Enhancement ◽  
System A ◽  
Single Column ◽  
The Impact

Traditional single-pixel imaging systems are aimed mainly at relatively static or slowly changing targets. When there is relative motion between the imaging system and the target, sizable deviations between the measurement values and the real values can occur and result in poor image quality of the reconstructed target. To solve this problem, a novel dynamic compressive imaging system is proposed. In this system, a single-column digital micro-mirror device is used to modulate the target image, and the compressive measurement values are obtained for each column of the image. Based on analysis of the measurement values, a new recovery model of dynamic compressive imaging is given. Differing from traditional reconstruction results, the measurement values of any column of vectors in the target image can be used to reconstruct the vectors of two adjacent columns at the same time. Contingent upon characteristics of the results, a method of image quality enhancement based on an overlapping average algorithm is proposed. Simulation experiments and analysis show that the proposed dynamic compressive imaging can effectively reconstruct the target image; and that when the moving speed of the system changes within a certain range, the system reconstructs a better original image. The system overcomes the impact of dynamically changing speeds, and affords significantly better performance than traditional compressive imaging.

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.

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