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Advanced Drift Diffusion Device Simulator for 6H and 4H-SiC MOSFETs

Advanced Drift Diffusion Device Simulator for 6H and 4H-SiC MOSFETs. MOSFET Device Structure. Semiconductor Equations. Poisson Equation:. Electron current continuity equation:. Hole current continuity equation:. Electron current equation:. Hole current equation:. MOSFET Device Simulation.

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Advanced Drift Diffusion Device Simulator for 6H and 4H-SiC MOSFETs

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  1. Advanced Drift Diffusion Device Simulator for 6H and 4H-SiC MOSFETs

  2. MOSFET Device Structure Semiconductor Equations Poisson Equation: Electron current continuity equation: Hole current continuity equation: Electron current equation: Hole current equation: MOSFET Device Simulation

  3. Low field mobility: Oxide Matthiessen's rule Electron Flow Bulk mLF = Low Field Mobility mB = Bulk Mobility mSP = Surface Phonon Mobility mSR = Surface Roughness mobility mC = Coulomb Scattering Mobility Electron Surface Phonon Trap Surface Roughness Fixed Charge High field mobility: Mobility Models High Field Mobility:

  4. Screened Coulomb Scattering Mobility Fermi’s Golden Rule: Screened Coulomb Potential: 2D Matrix Element: Scattering Rate: Screened Coulomb Scattering Mobility:

  5. ID-VGS at Room Temperature Circles : Simulated Points Line: Experimental data

  6. Occupied interface trap density Negatively charged interface traps: Dit = Interface traps density of states f(E) is the probability density function.

  7. Neutrality Point Interface Trap Density of States Figure . Interface trap density of states for 4H-SiC: Constant distribution in midgap and an exponential rise near the band edges.

  8. Mobility Variation with Depth VGS = 14V. Lots of Screening. Coulomb Mobility effect only very close to interface. Surface Roughness mobility dominates VGS = 2V. Less Screening. Coulomb Mobility dominates

  9. Current Density Variation with Depth Peak of the current density is some distance away from the interface

  10. Nit – VGS and Ninv – VGS at RmT Fixed Oxide Charge Density ~ 1.45e12 cm-2

  11. Screened Coulomb Scattering Mobility • Coulomb scattering decreases rapidly with increase in depth inside the semiconductor • Oxide charges located away from the interface have less effect on Coulomb scattering • Screening is directly proportional to the inversion layer charge density • Scattering rate is inversely proportional to electron temperature (energy) • Scattering rate is directly proportional to the density of oxide charges and occupied interface traps

  12. Future Work • Implement oxide charging - interface trap charging model in simulator • Implement a robust surface roughness mobility model • High temperature high power simulations • Modeling of different Power MOSFET structures

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