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  • a-IGZO TFT Simulation
    Density of State DOS Extraction General density of state in bulk a IGZO forbidden bandgap can be incorporated into Atlas TFT simulator For example total acceptor like traps is sum of deep state and shallow states as following equation 1 here g DA E is deep state and gTA E is shallow state red color in Figure 3 N DA and N TA is maximum traps concentration at E Ec The equivalent interface traps is defined as sum of donor like and acceptor like traps refer to Figure 3 2 The total donor like states in bulk a IGZO film is defined as sum of tail distribution from valence band edge and deep Gaussian function shape at fixed position with Eov left plot in Figure 3 blue color 3 Here gTD E is shallow trap from valence band edge and gov E is donor like with peak position energy of Eov Figure 3 shows simulation DOS and reference data These DOS were used to subsequent simulation task to see various effect on the electrical behavior Figure 3 Definition of DOS Density Of States in forbiden band gap of IGZO active left is bulk DOS in a IGZO channel region and right is a IGZO gate insulator interface trap Bottom plot is reference s extracted DOS by multifrequency CV analysis We simulated the dependence of donor like Gaussian traps on IDVG and IDVD Figure 4 When donor like Gaussian Nov here traps is increased then IDVG is shifted to negative gate bias direction and IDVD is rapidly increased to higher drain current When donor like traps is above 1e18 cm3 then simulated IDVG differs from reference result of analytical model It is related to a IGZO band gap and position of donor like traps If a IGZO band gap is fixed at 3 2eV as it can be seen in the DOS plot of reference paper paper 1 the most probable cause is different value of position of donor like trap Eov 2 9eV Figure 4 donor like Gaussian traps effect on IDVG and IDVD position of donor like traps is Eov 2 9eV left is three different donor like traps shape middle is corresponding IDVG and right is IDVD for each DOS When we adjust the peak position of Gaussian profile to lower value from the conduction band edge 0 15eV then we can reproduce the same trend of IDVG with different donor like trap Figure 4 1 The position of peak Gaussian is very sensitive parameter which decides overall device characteristics as shown in the simulation result Figure 4 1 Peak position of donor like traps is reduced from 2 9eV to 2 75eV and it shows the same trend as compare to reference 1 Figure 5 show the effect of acceptor like interface trap on IDVG shape Figure 5 interface trap dependence on IDVG left plots are reference data by analytical model and right is simulation result Figure 3 Definition of DOS Density Of States in forbidden band

    Original URL path: http://www.silvaco.fr/tech_lib_TCAD/simulationstandard/2016/jan_feb_mar/a1/a1.html (2016-05-03)
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  • Blue LED Simulation
    carrier density rate equations in the well regions becomes 3 4 In the 2D in plane quantum well regions net recombination rate is the sum of spontaneous emission rate and total capture escape rate Here x z plane is in quantum well in plane and y is assumed to be normal growth direction The 2D bound carrier density becomes 5 The bulk carrier density which is used to calculate the current density in the drift diffusion formalism is modified to consider this confined 2D carrier in the quantum well regions 6 The capture escape rate is calculated by following equation 7 Here tn is capture time in the well material well taun 1e 12 s well taup 1e 12 s To consider this additional 2D bound carriers we also have to consider SRH recombination as well Auger recombination in the well region Atlas takes into account these recombination in the quantum well regions including surface and interface trap recombination material capt augern 1e 31 capt augerp 1e 31 Auger in the well material capt srh n 1e 9 capt srh p 1e 9 SRH in the well inttrap qwell s i donor e level 0 2 density 1e12 interface trap interface s i s well n 1e3 s well p 1e3 surface recombination To activate above recombination we need to turn on following model flags model capt srh capt auger well capt well inplane well selfcon In the above model well inplane consider 2D in plane current density equation In the effective mass and parabolic approximation the radiative recombination in quantum well is 8 where r 2D m r h 2 L 2 is the two dimensional density of states m r is a reduced electron hole mass n r is a material refractive index I m n m n in a overlap integral of electron and hole wavefunctions Now when we consider this new capture escape model to the forward current dependence on number of quantum well as in section 2 3 the forward voltage shift is less pronounced as compared to Figure 2 If polarization is further decreased by taking into account of more defect screening effect or is zero then forward voltage change is less pronounced with increasing quantum well or no further forward voltage shift in 4QW case Figure 3 The carrier profile by capture escape model well explain why forward voltage is lower than by drift diffusion solution The carrier has some probability to penetrate into barrier regions which is much higher than in the case of non capture escape model Figure 4 Figure 3 Forward current behavior by capture escape model left figure shows IV shift by number of quantum well with 50 polarization of theoretical value and right figure shows less IV shift plot by number of quantum well without polarization Figure 4 carrier distribution at 200A cm2 left is without capture escape model and right figure show carrier distribution with capture escape model The carrier profile without capture escape model show that electron concentration in the barrier region is far below 1x10 10 cm 3 in 1st barrier and hole concentration is decreased to below 1x10 cm 3 at the 3rd barrier region But the carrier concentrations in the barrier by capture escape model is smoothly decayed from quantum well region and have 1x10 14 cm 3 in the first two quantum well barrier pairs We can conclude from this result that capture escape model accurately describe the exact carrier profile and so explain why drift diffusion solution always give high forward voltage when number of quantum well is increased 3 Material Growth and Trap Assisted Tunneling TAT So far we have used positive polarization scheme in which polarization is directed toward to bottom interface as in Ga face growth condition But polarity is still uncertain because it is very depending on which substrate buffer layer is used and also growth condition Figure 5 Polarity inversion by substrate and buffer layer The default polarity in Atlas uses positive convention which is positive charge at the bottom interface and negative charge at the top interface So direction of polarization is downward and built in electric field is opposite direction Figure 6 show that polarity inversion significantly affect on the forward voltage The actual amount of polarization by screening effect from various defects dislocation or V defect is very hard to estimate and optimize to fit the experimental forward current Most of simulation tasks so far normally use polarization between 20 and 80 from theoretical value but it is very broad range to adjust to fit forward current Figure 6 Forward current behavior by polarity red minus polarity blue positive polarity When we use polarization we should keep in mind that the polarization is globally scaled from theoretical calculation which is not true in actual polarization of each layer To simulate more accurate polar GaN LEDs it is very important to understand underlying polarization in each layer Also if non negligible traps in the quantum well exists there are some possibility that electron can tunnel from n side to p side region via trap assisted tunneling mechanisms For this purpose we simulated trap assisted tunneling to see the effect on forward tunneling current in single quantum well case Figure 7 show forward current behavior by existence of traps in quantum well regions and trap assisted tunneling effects in low bias regions In positive polarity case we can see the conventional trap assisted tunneling current at low bias range Figure 7 forward current behavior by donor trap and trap assisted tunneling red without traps and TAT blue with trap only light blue traps TAT Top plot is negative polarization case and bottom plot is positive polarization case 4 Band gap Reduction by Ambient Temperature We studied the ambient temperature effect on forward current because LED performance is significantly affected by operation temperature Normally high efficiency and high power LED operates in fairly high temperature above 300K and band gap reduction by temperature is very important

    Original URL path: http://www.silvaco.fr/tech_lib_TCAD/simulationstandard/2016/jan_feb_mar/a2/a2.html (2016-05-03)
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  • About Us
    transistors that power all consumer electronics Silvaco s mission is to help our customers accelerate the pace of technological innovation and their time to market while reducing their costs in developing the next generation chips that enable the digital revolution We strive to understand our customers challenges so as to tailor the innovative products services and support they need to address these challenges and succeed in their technology development and productivity goals In 1984 the initial product Utmost quickly became the industry standard for parameter extraction device characterization and modeling In 1985 Silvaco entered the SPICE circuit simulation market with SmartSpice In 1987 Silvaco entered into the Technology Computer Aided Design TCAD market By 1992 Silvaco became the dominant TCAD supplier with the Athena process simulator and Atlas device simulator In 1997 Silvaco entered the analog IC CAD market with a suite of EDA tools for schematic capture layout and physical verification DRC LVS and LPE In 2004 Silvaco entered the digital market offering tools for cell core library characterization place and route and Verilog simulation In 2006 Silvaco began to offer foundry specific PDKs to enable designers to streamline their design flows all the way to fabrication This began with the TSMC 0 18um process and has since grown to over ninety PDKs for eighteen foundries and the number of supported PDKs continues to grow In October 2012 after an extensive battle Dr Pesic succumbed to cancer Ownership of Silvaco remains in the Pesic family with Dr Pesic s son Iliya Pesic as Executive Chairman of the Board The company extended its alliances with the EDA and TCAD business communities and is a proactive member of such industry associations as Si2 SEMATECH CMC and GSA In 2015 Silvaco announced a new CEO David Dutton and executive management team with

    Original URL path: http://www.silvaco.fr/company/profile/profile.html (2016-05-03)
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  • SILVACO - Management Team
    UC Berkeley Amit Nanda Vice President Global Marketing Amit Nanda serves as the Vice President of Global Marketing for Silvaco Nanda has extensive experience in EDA marketing with an emphasis on SPICE simulation yield analysis and transistor level design as well as expertise in working within the foundry fabless ecosystem Prior to Silvaco Nanda served as a marketing director at ProPlus and Solido With a broad semiconductor technology background spanning wireless ASICs SoCs power devices analog IP and foundry services Nanda worked in product management business development applications and engineering roles at ArrayComm International Rectifier Barcelona Design Chartered Semiconductor and IC Works Nanda holds a MBA from Santa Clara University a M S in Electrical Engineering from Colorado State University and a B S in Electronics Engineering from University of Bombay Mark Maurer Vice President Business Development Foundry PDK Mark Maurer is the Vice President of Business Development for Silvaco s Foundry and PDK product areas Since joining Silvaco in 2000 Mauer assumed responsibility for all defense business and most recently served as the company s VP of Aerospace Defense Maurer holds a M S in Program Management from Regis University and a B A in Marketing Communications from Central College Dr Eric Guichard Vice President of the TCAD Division Dr Eric Guichard is Vice President of Silvaco s TCAD Division He is responsible for managing all aspects of the TCAD division from R D to field operations Since joining Silvaco in 1995 he has held numerous positions including director of Silvaco France and most recently Director of Worldwide TCAD Field Operations Prior to joining Silvaco Guichard was a senior SOI engineer specializing in transistor and circuit aging at LETI and Thomson Military and Space Dr Guichard holds an MS in material science and a Ph D in semiconductor physics

    Original URL path: http://www.silvaco.fr/company/management/index.html (2016-05-03)
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  • SILVACO - Corporate - Partners
    industry Foundry Partners Industry Associations University Partners EDA Partners IP Partners CORPORATE About Us News Management Partners Careers Conferences Goverment Programs Locations Contact Us Solutions Overview Display Power Reliability Optical Advanced Process Development Analog HSIO Design Library Memory Design Technical

    Original URL path: http://www.silvaco.fr/company/partners/partners.html (2016-05-03)
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  • Careers Opportunities Worldwide at Silvaco
    and professionals who are driving this growing 100 debt free self funded stable company CORPORATE About Us News Management Partners Careers Conferences Goverment Programs Locations Contact Us Solutions Overview Display Power Reliability Optical Advanced Process Development Analog HSIO Design Library

    Original URL path: http://www.silvaco.fr/company/openings/openings.html (2016-05-03)
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  • SILVACO - Government Programs
    unique requirements of our customers in the DoD DoE Intelligence Community and Other Government Agencies OGA Contact information Mark Maurer Vice President Government Business Division 10260 Campus Point Drive MSC4 San Diego CA 92121 M 408 318 1977 mobile E mark maurer silvaco com CORPORATE About Us News Management Partners Careers Conferences Goverment Programs Locations Contact Us Solutions Overview Display Power Reliability Optical Advanced Process Development Analog HSIO Design Library

    Original URL path: http://www.silvaco.fr/government/index.html (2016-05-03)
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  • SILVACO - Corporate - Locations
    California Texas Massachusetts Silvaco Japan Silvaco Europe Silvaco France Silvaco Korea Silvaco Taiwan Silvaco Singapore Silvaco China India M S Micro Chitronix Systems Cognitive Design Technology Pvt Ltd CDT Malaysia Pakistan and Middle East IC Microsystems CORPORATE About Us News Management Partners Careers Conferences Goverment Programs Locations Contact Us Solutions Overview Display Power Reliability Optical Advanced Process Development Analog HSIO Design Library Memory Design Technical Library Publications Webinars University Program

    Original URL path: http://www.silvaco.fr/company/offices/offices.html (2016-05-03)
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