Fermi-edge singularities in ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As and GaAs quantum wires

Strong Fermi-edge singularities (FES) were observed in the magnetoluminescence spectra of ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wires. The distinct shift of spectral weight and peaks at the Fermi energy are strongly temperature dependent, broadening and diminishing in intensity by T=30 K. The FES features shifted diamagnetically in applied magnetic fields, indicative of excitonlike bound states, while the rest of the electron gas was Landau quantized giving also a measure of the typical electronic wire widths of ${\mathit{L}}_{\mathrm{ww}}$≊500 Å. While the FES effects in the ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wires are associated with spatially direct transitions, aided by hole localization, we have also observed related effects in GaAs, where a Schottky-gate bias is needed to induce the effect due to the dominantly spatially indirect nature of the transitions.