FERMI-EDGE SINGULARITIES IN INXGA1-XAS AND GAAS QUANTUM WIRES

Strong Fermi-edge singularities (FES) were observed in the magnetoluminescence spectra of InxGa1-xAs 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 L(ww) almost-equal-to 500 angstrom. While the FES effects in the InxGa1-xAs 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.