Abstract
We describe an approach for fabricating high-quality Bi thin films and heterostructures on substrates by epitaxially growing them between layers of semiconducting . We present results from reflection high-energy electron diffraction, scanning electron microscopy, and atomic force microscopy analysis and show that the films are single crystalline with typical rms roughness of 1 nm and a dislocation density of 2× . Low-temperature magnetoresistance measurements are discussed in detail for a 90-nm /45-nm Bi/65-nm heterostructure. At liquid-helium temperatures, the electrical transport in the central, 45-nm-thick Bi layer is well described by a three-carrier model that takes into account high mobility electrons (=1.0× /V s) and holes (ν=3.1× /V s), as well as low mobility surface charges. The electron and hole densities are roughly equal and a factor of 6 higher than in the bulk. The epitaxial growth and clean interfaces result in a long electron elastic-scattering length, =0.38 μm. From an analysis of the observed Shubnikov–de Haas oscillations we obtain values for the extremal cross section of the Fermi surface, the cyclotron mass, and the single-particle relaxation time. At 45 nm the film thickness is comparable to the Fermi wavelength and, due to quantum confinement, only a few two-dimensional subbands of the electron pocket are filled.
- Received 13 January 1995
DOI:https://doi.org/10.1103/PhysRevB.52.5953
©1995 American Physical Society