QUANTUM WIRE STRUCTURES BY MBE OVERGROWTH ON A CLEAVED EDGE

We have recently demonstrated the existence of a high mobility (6.1 x 10(5) cm2/V.s) two-dimensional electron gas (2DEG) at the (110) vicinal surface formed by cleaving [L. Pfeiffer et al., Appl. Phys. Letters 56 (1990) 1697] a (100) GaAs wafer. We have now expanded this work to modulation-doped overgrowth on the cleaved edge of a multiperiod superlattice. We report here the first observation of the quantum Hall characteristics in such a two-dimensional system containing an atomically precise 71 angstrom GaAs by 31 angstrom Al0.24Ga0.76As compositional superlattice. The onset of Shubnikov-De Haas oscillations occurs at only 3000 G, implying the Landau cyclotron orbits are phase coherent over diameters as large as 5000 angstrom, corresponding to more than 200 GaAs/AlGaAs interface crossings.