32 research outputs found
Simulation study of silicon carbide Clustered Insulated Gate Bipolar Transistor (CIGBT)
Power semiconductor devices are inevitable parts of a power electronic converter system, with nearly 50% of electricity used in the world controlled by them. Silicon power devices have been used in power systems ever since the vacuum tubes were replaced by them in the 1950s. The performance of devices in a circuit is decided by the switching strategies and the inherent device performance like its on-state voltage, turn-on and turn-off times and hence their losses. Due to their inherent material properties, the growing interest in wide band gap devices is in applications beyond the limits of Si or GaAs. SiC is a wide bandgap material with properties that make it an attractive alternative to Silicon for high power applications.
Silicon Insulated Gate Bipolar Transistor (IGBT) is the most favourable device in the industry today for medium/high power applications. Silicon Clustered Insulated Gate Bipolar Transistor (CIGBT) is experimentally proven to demonstrate better performance as compared to their IGBT counterparts. In this work, the theoretical limit of silicon CIGBT is studied in great detail and compared to previously predicted IGBT limit. Later part of this thesis would explain the design and optimization of CIGBT in 4H- SiC. An in-depth simulation study of the same device is performed for both static and dynamic characteristics. Both planar and trench gate CIGBT devices are discussed here along with possible fabrication process. Along with this, a comparison study between CIGBT with its equivalent IGBT in SiC is also performed through extensive 2D simulations in MEDICITM in terms of their static and dynamic characteristics. Finally, a comparative study of P channel and N channel SiC CIGBT devices is evaluated through simulations
Recommended from our members
High Efficiency IGBTs through Novel Three-Dimensional Modelling and New Architectures
New Insulated Gate Bipolar Transistor (IGBT) designs are reliant on simulation tools, such as Sentaurus technology computer-aided design (TCAD) models, which allow for rapid device development that could not be achieved by manufacturing prototypes due to the cost and time associated with fabrication. These simulations are, though, computationally expensive and typically most design engineers develop these TCAD models only in two dimensions. This leads to inaccuracies in the model output since manufactured transistors are inherently three-dimensional (3D).
Based upon a commercial IGBT, this thesis begins by outlining the development of a 3D TCAD model using design details provided by the manufacturer. Large variations between the experimental data from the manufactured device and the simulation model lead to the discovery of widespread birds-beaking within the IGBT â an uncontrollable processing defect that the manufacturer was unaware of. This thesis presents a new simulation technique to account for this processing error while minimising computational effort and investigates the consequence of this birds-beak on the reliability of the device. The verified 3D IGBT model was also used to determine an optimum cell design that considered critical 3D effects omitted from previous studies.
An extensive literature review for the Reverse-Conducting IGBT (RC-IGBT) is provided. It is shown that despite the benefits of the RC-IGBT, the device suffers from many undesirable design trade-offs that have prevented its widespread use. The RC-IGBT designs that have currently been proposed in literature, either present a trade-off in performance, an inability to be manufactured, or a requirement for a custom gate drive. This thesis presents a new RC-IGBT concept, the âDual Implant SuperJunction (SJ) RC-IGBTâ that addresses these concerns and is manufacturable using current state of the art techniques. The concept and proposed manufacturing method enables, for the first time, a full SuperJunction structure to be achieved in a 1.2kV device.
In addition, an investigation into a coordinated switching scheme using both a silicon IGBT and silicon-carbide MOSFET was undertaken, which aimed to improve turn-off losses within the IGBT without sacrificing on-state losses. Thermal modelling of the power devices switching under inductive load was explored as the system was optimised to use a SiC MOSFET in excess of its nominal ratings, reducing the overall system cost.EPSRC Doctoral Training Partnership scheme (grant RG75686
Composite power semiconductor switches for high-power applications
It is predicted that 80 % of the worldâs electricity will flow through power electronic based converters by 2030, with a growing demand for renewable technolo gies and the highest levels of efficiency at every stage from generation to load. At
the heart of a power electronic converter is the power semiconductor switch which
is responsible for controlling and modulating the flow of power from the input to
the output. The requirements for these power semiconductor switches are vast,
and include: having an extremely low level of conduction and switching losses;
being a low source of electromagnetic noise, and not being susceptible to external
Electromagnetic Interference (EMI); and having a good level of ruggedness and
reliability. These high-performance switches must also be economically viable
and not have an unnecessarily large manufacturing related carbon footprint.
This thesis investigates the switching performance of the two main semiconductor switches used in high-power applications â the well-established Silicon
(Si)-Insulated-Gate Bipolar Transistor (IGBT) and the state-of-the-art Wide-Bandgap (WBG) Silicon-Carbide (SiC)-MetalâOxideâSemiconductor Field-Effect
Transistor (MOSFET). The SiC-MOSFET is ostensibly a better device than
the Si-IGBT due to the lower level of losses, however the cost of the device is
far greater and there are characteristics which can be troublesome, such as the
high levels of oscillatory behaviour at the switching edges which can cause serious Electromagnetic Compatibility (EMC) issues. The operating mechanism of these devices, the materials which are used to make them, and their auxiliary
components are critically analysed and discussed. This includes a head-to-head
comparison of the two high-capacity devices in terms of their losses and switching
characteristics. The design of a high-power Double-Pulse Test Rig (DPTR) and
the associated high-bandwidth measurement platform is presented. This test rig
is then extensively used throughout this thesis to experimentally characterise the
switching performance of the aforementioned high-capacity power semiconductor
devices.
A hybrid switch concept â termed âThe Diverterâ â is investigated, with
the motivation of achieving improved switching performance without the high-cost of a full SiC solution. This comprises a fully rated Si-IGBT as the main
conduction device and a part-rated SiC-MOSFET which is used at the turn-off.
The coordinated switching scheme for the Si/SiC-Diverter is experimentally examined to determine the required timings which yield the lowest turn-off loss and
the lowest level of oscillatory behaviour and other EMI precursors. The thermal stress imposed on the part-rated SiC-MOSFET is considered in a junction
temperature simulation and determined to be negligible. This concept is then
analysed in a grid-tied converter simulation and compared to a fully rated SiC-MOSFET and Si-IGBT. A conduction assistance operating mode, which solely
uses the part-rated SiC-MOSFET when within its rating, is also investigated.
Results show that the Diverter achieves a significantly lower level of losses compared to a Si-IGBT and only marginally higher than a full SiC solution. This is
achieved at a much lower cost than a full SiC solution and may also provide a
better method of achieving high-current SiC switche
Novel Power Electronic Device Structures for Power Conditioning Applications
The work presented in this thesis contains an investigation into the methods by which the semiconductor device performance can be improved with an aim to reduce the overall losses in the power conversion system. The types of devices discussed and evaluated in this thesis
include Silicon MOSFETs, IGBT, CIGBT and GaN HEMT devices. The performance improvement methods suggested in literature usually involve a trade-off of device characteristics with one another. Therefore an investigation into new device technologies and structures is deemed necessary such that the performance trade-off can be avoided or be improved
A Viable Residential DC Microgrid for Low Income Communities â Architecture, Protection and Education
The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems.
This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of âsmartâ appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future
A Viable Residential DC Microgrid for Low Income Communities â Architecture, Protection and Education
The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities with high unemployment and low wages, households contribute a significant portion of their income towards the fixed cost of their electrical utility connection, which by law must be supplied to every household. In order to realize such a microgrid in these communities, there are three major areas which need to be accounted for. Firstly, there needs to be a custom architecture for the community under consideration and it needs to be economical to match the needs of the underserved community. Secondly, DC microgrid for home energy interconnection is potentially less complex and less expensive to deploy, operate and maintain however, faster protection is a key element to ensuring resilience, viability and adoptability. Lastly, these types of efforts will be sustainable only if the people in the community are educated and invested in the same as they are the key stakeholders in these systems.
This dissertation presents an approach to make the DC Microgrid economically feasible for low income households by reducing the cost they incur on electric bills. The approach is to overlay a DC system into homes that have a utility feed in order to incorporate renewable energy usage into an urban setting for the express purpose of driving down individual household utility costs. The results show that the incorporation of a certain level of âsmartâ appliances and fixtures into the renovation of vacated homes and the use of a microgrid to enable sharing of renewable energy, such as solar power combined with energy storage, between homes in the proposed architecture yields the least expensive option for the patrons. The development of solid state circuit breakers that interface between the microgrid and the home DC power panels helps in faster protection of the DC system. In this dissertation, a SiC JFET based device is designed and built to protect against DC faults at a faster rate than the available solutions. The prototype is tested for verification and used to discriminate against short circuit faults and the results show the successful fault discrimination capabilities of the device. A basic system level simulation with the protection device is implemented using Real Time Hardware in the loop platform. Finally, as a part of engaging the community members, the high school kids in the area who might potentially be living in some of the houses in this community are being educated about the microgrid, appliances and other technologies to get a better understanding of STEM and hopefully inspiring them to pursue a career in STEM in the future
Optimization of power MOSFET devices suitable for integrated circuits
TĂĄto doktorskĂĄ prĂĄca sa zaoberĂĄ nĂĄvrhom laterĂĄlnych vĂ˝konovĂ˝ch tranzistorov s nĂzkym ĹĄpecifickĂ˝m odporom pri zapnutom stave, vhodnĂ˝ch pre integrĂĄciu do IntegrovanĂ˝ch Obvodov.This doctoral thesis deals with the design of lateral power transistor with lower specific on-resistance for integration into IC.The new model of MOSFET with waffle gate pattern is there described. For first, time the conformal transformation the Schwarz-Christoffel mapping has been used for the description of nonhomogeneous current distribution in the channel area of MOSFET with waffle gate pattern. In addition base on the figure of merit definition Area Increment (AI) the topological theoretical limit of MOSFET with waffle gate pattern has been a first time defined
Investigation of Gallium Nitride Based on Power Semiconductor Devices in Polarization Super Junction Technology
Over the last decade, gallium nitride (GaN) has emerged as an excellent material for
the next generation of power devices. GaN transistors, switching losses are very low,
thanks to the small parasitic capacitances and switching charges. Device scaling and
monolithic integration enable a high-frequency operation, with consequent
advantages in terms of miniaturization. For high power/high voltage operation, GaN�based Polarization Super-Junction (PSJ) architectures demonstrate great potential.
The aim of this thesis is devoted to the development of PSJ technology. Detailed
analysis of the on-state behaviour of the fabricated Ohmic Gate (OG) and Schottky
Gate (SG) PSJ HFETs is presented. Theoretical models for calculating the sheet
densities of 2DEG and 2DHG are proposed and calibrated with numerical simulations
and experimental results. To calculate the R (on, sp) of PSJ HFETs, two different gate
structures (Ohmic gate and Schottky gate) are considered herein.
The scaling tendency of power devices enables the emergence of multi-channel PSJ
concepts. Therefore, lateral and vertical multi-channel PSJ devices based on practical
implementation are also investigated. Presented calculated and simulated results
show that both lateral and vertical multi-channel PSJ technologies can be well suited
to break the unipolar one-dimensional material limits of GaN by orders of magnitude
and achieve an excellent trade-off between R (on, sp) and voltage blocking capability
provided composition and thickness control can be realised.
A novel multi-polarization channel is applied to realize normally-off and high�performance vertical GaN device devices for low voltage applications based on the
multi-channel PSJ and vertical MOSFET concepts. This structure is made with 2DHG
introduced to realize the enhancement mode channel instead of p-GaN as in
conventional vertical GaN MOSFETs. As the 2DHG depends upon growth conditions,
p-type doping activation issues can be overcome. The Mg-doped layer is only used to
reduce the short-channel effects, as the 2DHG layer is too thin. Two more 2DEG layers
P a g e | iv
are formed through AlGaN/GaN/AlGaN/GaN polarization structure, which
minimizes the on-state resistance. The calculation results show this novel vertical GaN
MOSFET â termed SV GaN FET - has the potential to break the GaN material limit in
the trade-off between R (on, sp) and breakdown voltage at low voltages. The
comprehensive set of development based on the PSJ concept gives a comprehensive
overview of next-generation power electronics