Monte Carlo analysis of carrier dynamics in GaN photoconductive switches for pulses in the 100 GHz range



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This work details calculations and simulations carried out to model charge carrier behaviors and transient photocurrent responses in Gallium Nitride (GaN) photoconductive semiconductor switches (PCSS). This was achieved using Monte Carlo analysis to adequately model semiconductor statistical processes such as elastic and inelastic scattering within a complex three valley GaN semiconductor band structure. A fast multipole solver is used to account for Coulomb forces between particles and polarization due to internal space-charge effects. Effects of charge screening in the PCSS are thus included, as are degeneracy and Pauli Exclusion effects that can restrict carrier scattering due to electron occupancies of final states. The input laser pulse is taken to have a Gaussian secant-hyperbolic temporal shape in keeping with experiments at Lawrence Livermore. Simulations are then used for proper modeling of carrier transport characteristics, the time-dependent photocurrent, transient electron distributions, and output pulse widths. Specific focus has been on the possibility of achieving pulse compression by utilizing a suitable external biasing and the negative differential mobility of GaN material.



Gallium Nitride, PCSS, Monte Carlo, Molecular Dynamics, Negative Differential Mobility, Pulse Compression