Scattering-assisted terahertz gain in semiconductor superlattices in the Wannier-Stark-Ladder regime

• Using the second-order perturbation theory we have calculated the scattering assisted gain spectra in GaAs/AlGaAs superlattice under a strong applied electric field in the Wannier-Stark-Ladder (WSL) regime. Nonequilibrium distribution function of quasi-two-dimensional carriers localized in each WSL level and indirect optical transitions between neighboring WSL levels accompanied by the emission or absorption of acoustical phonons are taken into account in our theoretical analysis and numerical calculation. We have shown that the experimentally observed down shift of the zero-gain frequency from the Bloch oscillation frequency is due to the inelastic nature of the phonon scattering and the formation of excitons when electron-hole pairs are photoexcited. Our theoretical results agree well with the experimental data which were obtained from analyzing the THz response of superlattices to the picosecond optical pulse excitation.

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NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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