Subband renormalization in dense electron-hole plasmas in ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As/InP quantum wires

${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As/InP quantum wires have been investigated by cw high-excitation luminescence spectroscopy. Quantum-wire states up to the edge of the InP conduction band have been populated in the dense neutral electron-hole plasma. Up to three lateral subband transitions are clearly observed in the luminescence spectra. By using calculated line shapes, the temperature and the density of the $e-h$ plasma as well as the band-gap reduction of the different lateral subbands have been determined. We observe a clear dependence of the renormalization on the subband index, which is traced to the density dependence of the exchange energy.