Observation and Analysis of a Non-Uniform Avalanche Phenomenon in 4H-SiC 4°-Off (0001) p-n Diodes Terminated with a Floating-Field Ring

2015 ◽  
Vol 821-823 ◽  
pp. 640-643 ◽  
Author(s):  
Kazuhiro Mochizuki ◽  
Hiroyuki Okino ◽  
Hiroyuki Matsushima ◽  
Yoshiaki Toyota
Keyword(s):  
Opposite Direction ◽  
Impact Ionization ◽  
Two Dimensional ◽  
Ionization Coefficient ◽  
Dry Oxidation ◽  
Aluminum Implantation ◽  
Dimensional Simulation ◽  
The Impact

4H-SiC (0001) p-n diodes terminated with a floating-field ring were found to emit light at breakdown in the opposite direction to that of substrate misorientation when the diodes were fabricated by aluminum implantation and dry-oxidation passivation. Two-dimensional simulation revealed that such non-uniform breakdown was mainly attributable to the asymmetric lateral straggling of implanted aluminum acceptors, rather than the anisotropic nature of the impact ionization coefficient.

Impact of Cavity on Sunroof Buffeting: A Two Dimensional CFD Study

2004 ◽  
Author(s):  
Chang-Fa An ◽  
Seyed Mehdi Alaie ◽  
Michael S. Scislowicz
Keyword(s):  
Fluid Dynamics ◽  
Wind Tunnel ◽  
Three Dimensional ◽  
Leading Edge ◽  
Two Dimensional ◽  
Deep Insight ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
The Impact ◽  
Insight Into

Driven by fluid dynamics principles, the concept for buffeting reduction, a cavity installed at the leading edge of the sunroof opening, is analyzed. The cavity provides a room to hold the vortex, shed from upstream, and prevents the vortex from escaping and from directly intruding into the cabin. The concept has been verified by means of a two dimensional simulation for a production SUV using the CFD software — FLUENT. The simulation results show that the impact of the cavity is crucial to reduce buffeting. It is shown that the buffeting level may be reduced by 3 dB by adding a cavity to the sunroof configuration. Therefore, the cavity could be considered as a means of buffeting reduction, in addition to the three currently-known concepts: wind deflector, sunroof glass comfort position and cabin venting. Thorough understanding of the buffeting mechanism helps explain why and how the cavity works to reduce buffeting. Investigation of the buffeting-related physics provides a deep insight into the flow nature and, therefore, a useful hint to geometry modification for buffeting reduction. The buffeting level may be further reduced by about 4 dB or more by cutting the corners of the sunroof opening into smooth ramps, guided by ideas coming from careful examining the physics of flow. More work including three dimensional simulation and wind tunnel experiment should follow in order to develop more confidence in the functionality of the cavity to hopefully promote this idea to the level that it can be utilized in a feasible way to address sunroof buffeting.

Modeling of a Breakdown Voltage in GaN Rectifiers and SiC Rectifiers

2001 ◽  
Vol 680 ◽  
Author(s):  
You-Sang Lee ◽  
Min-Koo Han ◽  
Yearn-Ik Choi
Keyword(s):  
Breakdown Voltage ◽  
Epitaxial Layer ◽  
Doping Concentration ◽  
Impact Ionization ◽  
Accurate Approximation ◽  
Ionization Coefficient ◽  
Zinc Blende ◽  
The Impact

ABSTRACTThe breakdown voltage of wurtzite and zinc-blende GaN rectifiers as function of a doping concentration and the width of epitaxial layer were successfully modeled in the reach-through case. The breakdown voltage was derived by the impact ionization integral employing the effective impact ionization coefficient and an accurate approximation. Our model shows that the breakdown voltage of wurtzite GaN rectifier was larger than those of zinc-blende GaN rectifier and SiC rectifiers including 4H-SiC and 6H-SiC in the condition that both the thickness and doping concentration of epitaxial layer are identical.

The Closed-Form Solutions For The Breakdown Voltages Of 6H-SiC Reachthrough Diodes

1998 ◽  
Vol 512 ◽  
Author(s):  
You-Sang Lee ◽  
D.-S. Byeon ◽  
Y.-I. Choi ◽  
I.-Y. Park ◽  
Min-Koo Han
Keyword(s):  
Closed Form ◽  
Breakdown Voltage ◽  
Epitaxial Layer ◽  
Doping Concentration ◽  
Impact Ionization ◽  
Analytic Solutions ◽  
Ionization Coefficient ◽  
Closed Form Solutions ◽  
The Impact ◽  
Effective Ionization

ABSTRACTThe closed-form analytic solutions for the breakdown voltage of 6H-SiC RTD, reachthrough diode, having the structure of p+-n-n+, are successfully derived by solving the impact ionization integral using effective ionization coefficient in the reachthrough condition. In the region of the lowly doped epitaxial layer, the breakdown voltages of 6H-SiC RTD nearly constant with the increased doping concentration. Also the breakdown voltages of 6H-SiC RTD decrease, in the region of the highly doped epitaxial layer, which coincides with Baliga'seq. [1].

Impact ionization threshold energy of trigonal selenium: An ab initio study

2013 ◽  
Vol 91 (6) ◽  
pp. 483-485 ◽  
Author(s):  
A. Darbandi ◽  
O. Rubel
Keyword(s):  
Impact Ionization ◽  
Threshold Energy ◽  
Charge Carriers ◽  
Ionization Threshold ◽  
Ab Initio Study ◽  
Ionization Coefficient ◽  
Semiconducting Material ◽  
Band Dispersion ◽  
Crude Approximation ◽  
The Impact

Impact ionization coefficient is a critical parameter that determines the multiplication gain in avalanche photodiodes. The impact ionization coefficient is closely related to the ionization threshold, Eth, which is determined by the band dispersion of the semiconducting material used in detectors. The ionization threshold energy is commonly calculated based on a parabolic band assumption, which provides only a crude approximation. Here we present a first principle study of the ionization threshold energy through an analysis of the electronic structure of trigonal selenium. It is shown that the excess energy of primary charge carriers required to initiate the impact ionization in trigonal selenium can be as low as the band gap, Eg, which is a sharp contrast to the parabolic band approximation that implies Eth = 3/2Eg. Such a low Eth value is a favourable factor for impact ionization.

Low-voltage Avalanche Breakdown in AlGaN Multi-quantum Wells

2006 ◽  
Vol 955 ◽  
Author(s):  
Shengkun Zhang ◽  
X. Zhou ◽  
Wubao Wang ◽  
R. R. Alfano ◽  
A. M. Dabiran ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Electric Fields ◽  
Impact Ionization ◽  
Low Voltage ◽  
Defect Density ◽  
Control Sample ◽  
Avalanche Breakdown ◽  
Ionization Coefficient ◽  
The Impact ◽  
Injection Modes

ABSTRACTIn this work, electro-luminescence (EL) of a AlGaN p-i-n diode have been investigated in both avalanche and injection modes. The active i-region of the diode consists of Al0.1Ga0.9N/Al0.15Ga0.85N MQWs. Strong interband luminescence from the Al0.1Ga0.9N active layers was observed when operating the device in both avalanche and injection modes. The threshold voltage for avalanche breakdown is as low as 9 V. This indicates that the impact ionization coefficient of electrons is greatly enhanced in these Al0.1Ga0.9N/Al0.15Ga0.85N MQWs comparing to AlGaN bulk materials. Polarization-induced electric fields in the Al0.1Ga0.9N well layers are believed to be responsible for the enhancement of the ionization coefficient. In a control sample that has higher defect density, the electroluminescence was dominated by long-wavelength emissions, which results from impact ionizations of the defect levels.

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