The practical application of Bloch oscillations in semiconductor superlattices as THz emitters is hampered by the low emission power and the rapid dephasing of the coherent signal. At higher excitation densities the quadratic scaling of the THz emission power saturates due to the stronger dephasing of the signal. We adopt an approach previously employed for the investigation of the dephasing of interband dynamics in four wave mixing to study the dephasing of the intraband dynamics responsible for the THz emission. We demonstrate that for higher carrier densities the dominant dephasing process at low temperatures is carrier-carrier scattering. The experiments are performed on a superlattice consisting of 9.7-nm GaAs wells separated by 1.7-nm AlGaAs barriers.
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