Growth of (Al,Ga)As quantum wells on (110)-GaAs by MBE

One dimensional devices which exhibit quantum mechanical effects are normally fabricated using epitaxial deposition to form a `two-dimensional gas´ (2-deg) of carriers followed by a lithographic process to further confine the carriers to one dimension of freedom. In order to observe these effects the quantum confinement and hence the structure must be uniform. Molecular beam epitaxy (MBE) can provide layer thickness control to within a few atomic layers whereas the highest resolution lithography is presently limited to a fraction of a micron or a few hundred atoms. Therefore it is difficult to define precise quantum wires in an epitaxial layer by lithographic methods. An alternative is the use of gate electrodes to confine conduction by depletion to a thin channel but this is sensitive to non-uniform electric fields. The authors investigate growth on to (110)-GaAs with the objective of defining one-dimensional structures using only growth. This involves the deposition of a multilayer structure on a (100) wafer which is then cleaved in vacuum to expose a (110) edge. A second structure is grown on to this edge and the one-dimensional confinement occurs at the junction between the new and the original layers. A number of devices can potentially be made by this method, including an addressable phased array of quantum wire lasers and an array of electronic quantum wires