The fabrication and optical properties of quantum wires.

Abstract

Chemical beam epitaxy was used to grow GaAs and InP based heterostructures on selectively masked substrates. The natural tendency of crystals to form facets was studied as a function of growth conditions. By exploiting this tendency, patterns were reduced from ${\sim}1$ micron in width to ${\sim}20$ nm in width, and inverted-V crescent quantum wire structures were grown entirely in situ. Photoluminescence spectra were obtained, showing broad multiple peaks which are related to the structure and migration between facets. Redshifts of over 100 meV were obtained for narrow structures. Mesa roughness and PL line width are identified as difficulties for the fabrication technique. A simple analytic model--the only separable model in two dimensions showing geometrical quantum confinement--is developed in the spirit of the Ben-Daniel Duke approximation for a square well. The model is applied to variational estimates for the exciton binding energy in crescent quantum wire structures and is compared to the experimental data.