Molecular beam epitaxy growth over shadow edges: a new method for in situ growth of nanostructures
We propose a new method to obtain well defined nanostructures in situ during MBE growth. The method is based on the MBE growth over UHV compatible shadow edges. These edges define a geometrical shadow region which can be modified by tilting the sample with respect to the direction of the molecular beams, so that layers with different lateral extension can be combined to form a buried junction of two quantum wells in the form a wire with lateral confinement. We show for ZnSe quantum wells in ZnMgSSe that the formation of facets at the shadow edge favours the formation of geometrically well defined structures, and quantum well junctions as narrow as 150 nm have been realized. The wires emit pronounced blue cathodoluminescence at room temperature, proving that even for simple structures the confinement of carriers in the resulting wire is on the order of kT at room temperature.