| 1. |
- Bertilsson, Kent, et al.
(författare)
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Monte Carlo simulation of vertical MESFETs in 2H, 4H and 6H-SiC
- 2001
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Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:3-7, s. 1283-1286
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Tidskriftsartikel (refereegranskat)abstract
- The 4H-SiC static induction transistor (SIT) is a very competitive device for high frequency and high power applications (3-6 GHz range). The large breakdown voltage and the high thermal conductivity of 4H-SiC allow transistors with extremely high current density at high voltages. The SIT transistor shows better output power capabilities but the unity current-gain frequency is lower compared to a MESFET device. In this work we show, using a very accurate numerical model, that a compromise between the features given by the SIT structure and the ordinary MESFET structure can be obtained using the vertical MESFET structure. The device dimension has been selected very aggressively to demonstrate the performance of an optimized technology. We also present results from drift-diffusion simulations of devices, using transport parameters obtained from the Monte Carlo simulation. The simulations indicate that 2H-SiC is superior to both 4H and 6H-SiC for vertical devices. For lateral devices, 2H-SiC is slightly faster compared to an identical 4H-SiC device
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| 2. |
- Bertilsson, Kent, et al.
(författare)
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The Effect of Different Transport Models in Simulation of High Frequency 4H-SiC and 6H-SiC Vertical MESFETs
- 2001
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Ingår i: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 45:5, s. 645-653
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Tidskriftsartikel (refereegranskat)abstract
- A full band Monte Carlo (MC) study of the high frequency performance of a 4H-SiC Short channel vertical MESFET is presented. The MC model used is based on data from a full potential band structure calculation using the local density approximation to the density functional theory. The MC results have been compared with simulations using state of the art drift-diffusion and hydrodynamic transport models. Transport parameters such as mobility, saturation velocity and energy relaxation time are extracted from MC simulations
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| 3. |
- Hjelm, Mats, et al.
(författare)
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Critical evaluation of scattering models within the full band Monte Carlo simulation framework
- 2005
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Ingår i: Recent Advances in Multidisciplinary Applied Physics. - : Elsevier. - 9780080446486 ; , s. 305-311
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The full band Monte Carlo (MC) simulation framework is regarded as the most accurate method available to study high-field carrier transport in semiconductors. Its potential has been demonstrated in a large number of studies over the years. In this work we focus on how the quantum mechanical uncertainty at high scattering rates affects the validity Fermi's Golden Rule, which traditionally is the basis for the scattering handling in the MC method. Considering the uncertainty is important in for instance silicon carbide, which at moderate energies exhibits a scattering rate exceeding 1014 s-1. The expression for time-dependent scattering rate is presented together with calculated rates for some initial states with acoustic as well as polar-optical phonon interaction. A first-order time-dependent algorithm for handling of scattering events in MC simulators is proposed.
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| 4. |
- Hjelm, Mats, et al.
(författare)
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Full band Monte Carlo simulation of cubic and hexagonal silicon carbide polytypes and devices
- 2004
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T114, s. 61-65
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Tidskriftsartikel (refereegranskat)abstract
- The GEMS (General Monte Carlo Semiconductor) simulator is a full band ensemble program developed at Mid-Sweden University. A principal objective of the project is to create a flexible tool that can be used for the exploration of properties of new semiconductor materials as well as devices fabricated of these materials. Both cubic and hexagonal crystal symmetries can be handled with the simulator, and any material with these symmetries can be simulated if an appropriate electronic band structure together with the parameters for the scattering mechanisms is provided. During the development of GEMS a large number of studies have been performed of bulk charge transport and device characteristics. The simulated materials are 2H-, 3C-, 4H- and 6H-SiC, as well as silicon. This presentation discusses the charge transport properties of the studied SiC polytypes, and the resulting performance of the simulated devices.
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| 5. |
- Martinez, Antonio, et al.
(författare)
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Scattering probabilities for multiband hole states at high electric fields and high collision rates in 4H-SiC
- 2004
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Ingår i: SILICON CARBIDE AND RELATED MATERIALS 2003, PTS 1 AND 2. - STAFA-ZURICH : TRANS TECH PUBLICATIONS LTD. ; , s. 1237-1240
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Konferensbidrag (refereegranskat)abstract
- The scattering probabilities for a multiband carrier wave function have been studied for hole transport in 4H-SiC. During the drift at high electric fields it is possible to find the carriers with almost equal probability in two neighboring bands. In contrast to the standard Monte Carlo procedure, a possible interference between the components of the wave function in different bands appears in the calculation of the scattering probabilities when the time between scattering events is short. An important role is played by the overlap integral, which forbids this interference in some regions of the epsilon-k (energy-wavevector) space. We compare the results obtained using the true overlap integrals calculated from the wave functions with the common assumption, in which the overlap integral is assumed equal to one. Different scattering mechanisms, such as polar-optical phonon and intervalley optical phonon are studied. The model includes a spread in energy according to the Heisenberg uncertainty principle at short times. We have calculated the final state probability distribution considering the whole Brillouin zone of 4H-SiC for a particular set of initial states.
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| 6. |
- Nilsson, Hans-Erik, et al.
(författare)
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Full band Monte Carlo simulation-beyond the semiclassical approach
- 2004
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Ingår i: Monte Carlo Methods and Applications. - : Walter de Gruyter GmbH. - 0929-9629 .- 1569-3961. ; 10:3-4, s. 481-490
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Tidskriftsartikel (refereegranskat)abstract
- A quantum mechanical extension of the full band ensemble Monte Carlo (MC) simulation method is presented. The new approach goes beyond the traditional semi-classical method generally used in MC simulations of charge transport in semiconductor materials and devices. The extension is necessary in high-field simulations of semiconductor materials with a complex unit cell, such as the hexagonal SiC polytypes or wurtzite GaN. Instead of complex unit cells the approach can also be used for super-cells, in order to understand charge transport at surfaces, around point defects, or in quantum wells.
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