Plasmons in deep etched quantum wires

Abstract

Employing deep reactive ion etching, we have realized narrow doped quantum wire arrays with lateral dimensions down to 60 nm and wires with periodic modulation of the width along the wire axis. The wire systems are characterized by means of inelastic light scattering from confined plasmons. These modes display unique Raman selection rules which we explain by taking into account both the polarization and the parity of the local electric field distribution in the wires. Lateral electric widths and carrier densities of the wires are deduced from the comparison of the plasmon dispersion with classical models. The electric widths are found to equal the geometrical ones, and the densities are comparable to the initial one of the unpatterned sample. Opening of forbidden gaps in the plasmon dispersion is observed in the presence of a width modulation and is quantitatively described in the frame of a classical model. This constitutes clear evidence, in contradiction to previous reports based on magneto-transport and microwave transmission, of the absence of lateral depletion in our experimental conditions.