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Conduction (a) and valence (b) band structures of one period of the active region calculated using a self-consistent Schrödinger-Poisson solver at per stage, with a 66% conduction band offset. Starting from the injection barrier, the layer sequence of one period, in nanometers is (from right to left): . AlGaAs layers are shown in bold, and the underlined GaAs wells are doped at . The shaded area and represents the lowest energy and the second minibands, respectively. The wave function square modulus of the excited laser state is labeled as . (c) and (d) Voltage and emitted power as a function of current measured in cw at different heat sink temperatures, for samples (c) and (d).
Representative photoluminescence spectra of samples [(a) and (c)] and [(b) and (d)] measured at device off [(a) and (b)] and at [(c) and (d)], at . The arrows labeled with mark the energies of the transitions between levels in the conduction minibands and valence subbands [see Figs. 1(a) and 1(b)]. The arrows marked with and indicate the heavy-hole and light-hole exciton peaks.
(a) Peak energy of the PL band labeled with plotted as a function of P for samples (●) and (▾). The lines are guides for the eye. (b) peak energy () calibration curve of sample A obtained as described in the text. The calibration curve of sample is identical.
Mean lattice temperature (∎) and miniband electronic temperatures (●), (▾) measured in the active region of the investigated device as a function of P, at for samples A (a) and B (b). The lines are linear fits to the data. The shaded areas mark the lasing region.
Comparison between the thermal resistances and the parameter of a set of investigated THz QCLs, classified on the base of the emission frequency and waveguide configuration.
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