Toward quantum well wires: Fabrication and optical properties

As a first step toward the realization of a one-dimensional carrier confining structure in semiconductors, we have fabricated GaAs quantum well wires (QWW) with submicron dimensions using molecular beam epitaxy of GaAs and Ga1−xAlxAs. The structural quality and dimensions of the QWW have been assessed by transmission electron microscopy showing that single crystal, defect-free QWW, with dimensions as small as 200×200 Å in cross section can be achieved. The optical properties measured by low-temperature (T≳20°K) cathodoluminescence (CL) indicate a CL efficiency nearly as good as that of the quantum well material from which the QWW originated. A localization of the luminescence along the QWW axis is characteristic of QWW with sizes below a critical dimension (1.5 μm×200 Å cross section). This luminescence localization and a shift of the intrinsic luminescence to lower energy in QWW structures are tentatively assigned to strain effects in these structures.