We introduce a two-fluid mobility model incorporating fundamental aspects of electron-hole (e-h) scattering such as momentum conservation for simulating laser-driven semiconductor switches (LDSSs). Compared to previous works that use Matthiessen’s rule, the two-fluid mobility model predicts distinct ac responses of e-h plasmas in semiconductors. Based on the two-fluid mobility model, we develop a theory with very few adjustable parameters for simulating the switching performance of LDSSs based on high-purity indirect-gap semiconductors such as silicon ($\mathrm{Si}$). As a prototypical application, we successfully reproduce experimentally measured reflectance at around 320 GHz in a laser-driven $\mathrm{Si}$ switch. By injecting e-h plasmas with densities up to ${10}^{20}{\mathrm{cm}}^{-3}$, we reveal the importance of carrier-screening effects in e-h scattering and Auger recombination for carrier densities above the critical carrier density for exciton-plasma Mott transition. Our results also suggest a way to characterize the intrinsic momentum-relaxation mechanism, e-h scattering, and the intrinsic e-h recombination mechanism in indirect-gap semiconductors, Auger recombination. We reassess the ambipolar Auger coefficient of high-purity $\mathrm{Si}$ with high injection levels of e-h plasmas up to ${10}^{20}{\mathrm{cm}}^{-3}$ and find a minimal value of $1.8\times {10}^{-41}{\mathrm{cm}}^6/\mathrm{ns}$. This value is more than one order of magnitude smaller than the ambipolar Auger coefficient widely used for simulating LDSSs, $3.8\times {10}^{-40}{\mathrm{cm}}^6/\mathrm{ns}$, which was deduced from the minority-carrier lifetime in highly doped silicon more than four decades ago.

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• Carrier generation & recombination
• Light-matter interaction
• Optoelectronics
• Photoinduced effect
• Devices
• Elemental semiconductors
• Plasma kinetic theory
• Two-fluid & multi-fluid model