Interaction between the Fermi-edge singularity and optical phonons in ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/{\mathrm{In}}_y{\mathrm{Ga}}_{1-y}\mathrm{As}/\mathrm{GaAs}$ heterostructures

Many-electron effects in pseudomorphically strained modulation-doped ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{\mathrm{A}\mathrm{s}/\mathrm{I}\mathrm{n}}_y{\mathrm{Ga}}_{1-y}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ $(x=0.20,\hspace{0.5em}y=0.19)$ heterostructures are investigated using photoluminescence as a function of magnetic field B, temperature T, and excitation density I. The interaction of the many-body exciton (Fermi-edge singularity) with the longitudinal–optical-phonon is observed. Both the Fermi-edge singularity and the enhancement of the exciton-longitudinal optical phonon interaction can be controlled by varying the magnetic field; the strengths of these two many-body effects change with filling factor. They are synchronous both with each other and with the resonance of the upper Landau level with the Fermi level. The strength of this phonon replica when the Fermi level is resonant with a Landau level is attributed to the magnetic-field-dependent screening properties of the two-dimensional electron gas in the quantum well.