Direct molecular beam epitaxial growth of low-dimensional structures on reactive ion etched surfaces

Quasi-one-dimensional GaAs structures were fabricated by molecular beam epitaxial regrowth on dry etched (AlGa)As surfaces, making use of the “self-adjusted” facetted growth on structured surfaces. The increased migration lengths and decreased sticking coefficients of the ad-atoms on higher indexed crystal planes lead to the formation of triangular, sharply peaked ridges with perfectly smooth sidewalls, having lateral dimensional fluctuations on the atomic scale over lengths of several 100 μm. The epitaxial deposition of a quantum well, i.e. a thin GaAs layer between (AlGa)As barriers, results in the direct growth of one-dimensional quantum wire structures at the vertex of the peaked ridges. The size of the GaAs wires can be controlled by the amount of Ga deposited between the (AlGa)As barriers. These one-dimensional structures show high yield in cathodoluminescence, without spectral shift over regions of hundreds of microns. Additional peaks in the CL spectra demonstrate the two-dimensional confinement of the quantum wires. Three-dimensionally confined quantum dots, also showing high luminescence yield, were found at the top of pyramidal structures grown on square mesas.