Figure 1

Raman intensities of the collective modes propagated (a) perpendicular and (b) parallel to the layers measured at $T=80\mathrm{K}$ in the $(\mathrm{GaAs}{)}_m({\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.7}\mathrm{As}{)}_6$ superlattice with the disorder strength ${\delta }_{\mathrm{SL}}=0.8$. The calculated contributions of the asymmetrical plasmonlike peaks are shown by thick lines. (c) The parallel and vertical magnetoresistances measured in the same superlattice at $T=1.6\mathrm{K}$. The dashed lines were calculated. Insets: the Hall bar and the double superlattice mesa used for the parallel and vertical transport measurements, respectively.Reuse & Permissions

Figure 2

Energy spectra of the vertically propagated single-particle (inset) and collective excitations calculated in the $(\mathrm{GaAs}{)}_{17}({\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.6}\mathrm{As}{)}_6$ superlattice with the electron concentration $n=2.0\times {10}^{17}{\mathrm{cm}}^{-3}$. The dashed and full lines represent the dispersions of the uncoupled plasmons and the plasmons coupled to the LO phonons, respectively. Thin lines show the dispersions of the single-particle (dotted line) and collective excitations (full lines) propagated parallel to the layers. The vertical dash-dotted line demonstrates the wave number transferred by the light used for excitation. The left panel shows the corresponding calculated Raman intensities obtained by the fits as explained in the text.Reuse & Permissions

Figure 3

(a) Raman intensity measured at $T=10\mathrm{K}$ in the $(\mathrm{GaAs}{)}_m({\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.6}\mathrm{As}{)}_6$ superlattice with the disorder strength ${\delta }_{\mathrm{SL}}=0.4$. (b) Weak-field vertical transversal magnetoresistance measured in the same superlattice at $T=10\mathrm{K}$ (labeled as DSL). The dashed lines were calculated. The data marked as GaAs relate to the mesa structure fabricated on the same doped substrate without the superlattice.Reuse & Permissions

Figure 4

Energy spectra of the vertically propagated single-particle (inset) and collective excitations calculated in the $(\mathrm{GaAs}{)}_{17}({\mathrm{Al}}_{0.3}{\mathrm{Ga}}_{0.6}\mathrm{As}{)}_6$ superlattice with the electron concentration $n=6.5\times {10}^{17}{\mathrm{cm}}^{-3}$. The dashed and full lines represent the dispersions of the uncoupled plasmons and the plasmons coupled to the AlAs LO phonons, respectively. The vertical dash-dotted line demonstrates the wave number transferred by the light used for excitation. The right panel shows the calculated Raman intensity obtained by the fit as explained in the text.Reuse & Permissions