We have fabricated and analyzed high quality InGaAs/InP quantum wires by electron beam lithography and wet chemical etching. In order to optimize the shape of the wet-etched wires different wire orientations were investigated. As results of the lithography process we obtain wire masks with widths down to 15 nm and etched wires with widths of the InGaAs layer of 18 nm.
The wires were studied optically by means of photoluminescence spectroscopy. In contrast to dry etched wire structures the wet chemically etched wires show strong optical emission even for geometrical widths less than 25 nm. The weak decrease of the quantum efficiency with decreasing wire width indicates that there are no dead layers at the side walls of the wires, which is in contrast to previous studies on dry-etched structures. The photoluminescence energy of the InGaAs/InP wires is independent of the wire dimension down to widths of 50 nm. This indicates that a steep lateral potential in our structures is obtained due to the confinement by the semiconductor/vacuum transition at the etched surfaces. For wires with smaller widths an increasing blue shift of photoluminescence energy up to more than 30 meV is observed.