Morphology of InGaAs/GaAs quantum wires prepared by highly controlled deep-etching techniques

Artikel i vetenskaplig tidskrift, 2001

Different types of InGaAs/GaAs deep-etched quantum wire (QWI) structure were successfully fabricated by high-energy electron beam lithography on GaAs(100) surfaces. A selective wet-chemical-etching technique, preceded by chemically assisted ion-beam etching, reduced the controlled lateral dimensions of the wires to ~10 nm due to strong under-etching. Various types of wire in the [011] and [011] crystallographic directions were prepared by the combined etching method. The side-walls of the wires were defined by the selectively etched low index crystallographic planes. A molecular-beam-epitaxy-grown graded InGaAs/GaAs quantum well was realized at the narrow `neck' region of the wires, thus providing the strongest possible lateral confinement of the QWI structure. Consequently, similarly to the selective growth of self-narrowing ridge structures, selective wet-chemical etching induced a controlled self-narrowing of the wire structures. Scanning electron microscopy images of the QWI nanostructures showed smooth side-walls defined by the crystallographic planes. Low-excitation photoluminescence spectroscopy of the structures revealed extremely high quantum efficiency and a size-dependent blue shift as a result of the strong lateral confinement