Shear strains in dry etched GaAs/AlAs wires studied by high resolution x-ray reciprocal space mapping

Abstract

We have fabricated GaAs/AlAs quantum wires and quantum dots by means of molecular beam epitaxy, electron beam lithography, and subsequent reactive ion etching using SiCl4 and O2. The nominal periods are 300 nm and 350 nm for both wire and dot samples. High resolution x-ray reciprocal space maps of the 350 nm samples exhibit not only satellites corresponding to a periodicity of 350 nm but also additional satellites corresponding to a period of three times 350 nm, whereas there are no such extra peaks in the maps of the 300 nm samples. These secondary satellites are shown to be associated with a discretization effect in electron beam writing. Moreover, we found, that the shear strain in the wires has a distinct influence on the intensities of these weak extra satellites. Hence, they provide a sensitive means for the assessment of shear strains in elastically relaxed quantum wires.