Photoluminescence excitation study of lateral-subband structure in barrier-modulated ${\mathrm{In}}_{0.09}$${\mathrm{Ga}}_{0.91}$As quantum wires

Barrier-modulated ${\mathrm{In}}_{0.09}$${\mathrm{Ga}}_{0.91}$As/GaAs quantum wires with widths down to 18 nm have been studied by photoluminescence and photoluminescence excitation spectroscopy. Up to three transitions arising from different laterally confined electron and hole subbands were observed for varying wire widths in photoluminescence excitation experiments. The experimentally determined dependence of the transitions of the three subbands on the wire width is described well by detailed calculations made using the geometrical dimensions of the wires.