Simulation of Si and GaAs submicron TRAPATT diodes

Abstract

Plasma formation and extraction processes in submicron silicon N⁺NP⁺, GaAs N⁺NP⁺, and GaAs NM Schottky TRAPATT (TRApped Plasma Avalanche Triggered Transit) diodes were simulated. The simulation of GaAs TRAPATT diodes was done for the first time. The quasi-hydrodynamic model was chosen for the simulation of the processes. The Synopsys TCAD Sentaurus Software Package was used. The carrier mobility dependence on phonon scattering, impurity scattering, carrier-carrier scattering, intervalley scattering (for GaAs), and mobility saturation in a high electric field was taken into account. Several generation-recombination mechanisms were included: impact ionization, Shockley–Read–Hall recombination (SRH) with doping-dependent lifetimes, trap-assisted tunnelling, band-to-band tunnelling, Auger recombination, and radiative recombination (for GaAs). We show that the so-called critical current density for plasma formation in the submicron diodes increases with the active layer thickness decrease and almost does not depend on the doping density in the active layer. The critical current density for silicon diodes is about two times lower than for the GaAs diodes. The intensive minority carrier storage in the N⁺ and P⁺ regions has a high influence on the voltage oscillation amplitude and frequency after the first plasma formation and extraction period. Oscillation damping takes place in the N⁺NP⁺ GaAs diode with the active layer thickness of less than 0.3 µm.