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Simulation of Current Filaments in Photoconductive Semiconductor Switches

Simulation of Current Filaments in Photoconductive Semiconductor Switches. K. Kambour, H. P. Hjalmarson, F. J. Zutavern and A. Mar Sandia National Laboratories* Charles W. Myles** Texas Tech University 15 th International IEEE Pulsed Power Conference June 16, 2005.

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Simulation of Current Filaments in Photoconductive Semiconductor Switches

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  1. Simulation of Current Filaments in Photoconductive Semiconductor Switches K. Kambour, H. P. Hjalmarson, F. J. Zutavern and A. Mar Sandia National Laboratories* Charles W. Myles** Texas Tech University 15th International IEEE Pulsed Power Conference June 16, 2005 * Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the United States Department of Energy under contract DE-AC04-94AL85000. ** Supported in part by an AFOSR MURI Contract

  2. Outline • Photoconductive Semiconductor Switches(PCSS's) • Lock-on • Collective Impact Ionization Theory • Monte Carlo Calculations • Continuum Calculations • Conclusions

  3. A PCSS

  4. Lock-on • Characterized by a persistent or 'locked-on' electric field (~5 kV/cm) after laser turn off. • High conductivity state • Always accompanied by the formation of current filaments. • The lock-on field is much lower than the bulk breakdown field for GaAs.

  5. Current Filaments

  6. Bistable Switch

  7. Carrier Distribution Function

  8. Collective Impact Ionization Theory Explains highly conductive filaments sustained by a lock-on field lower than the breakdown field. • Inside (high carrier density): the carrier-carrier scattering increases the efficiency of impact ionization for the hot carriers. • Outside (low carrier density): the electric field is too low to create carriers by impact ionization.

  9. Monte Carlo Calculations Calculating the rate of change of particle number Determining the distribution function Ensemble Monte Carlo Maxwellian

  10. Evolution to a Steady State Solution(no carrier-carrier scattering)

  11. Steady State Solution(no carrier-carrier scattering)

  12. Evolution to Steady State Solutions(carrier-carrier scattering included)

  13. Steady State Solutions(carrier-carrier scattering)

  14. GaAs

  15. Continuum Calculations

  16. Continuum Results

  17. Continuum Results

  18. Conclusions • Collective Impact ionization Theory (CIIT) predicts that lock-on will occur in GaAs at a field much less than the intrinsic breakdown field in GaAs, in qualitative agreement with experiment. • CIIT also predicts that the lock-on field will be independent of rise time and that the lock-on current will flow in stable current filaments in agreement with experiment.

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