SUBBAND MIXING IN RESONANT MAGNETOTUNNELING THROUGH DOUBLE-BARRIER SEMICONDUCTOR NANOSTRUCTURES

We investigate subband mixing in the magnetotunneling of an electron t hrough a double-barrier quantum dot. The fine structure in the current -voltage characteristics, observed in a device formed by a quantum-dot sandwiched by two quantum-wire contacts, is studied as a function of a magnetic field applied along the direction of the tunneling current. The increase of the magnetic field in this one-dimensional-zero-dimen sional-one-dimensional tunneling process leads to a transition from a low-field regime dominated by lateral confinement to a high-field regi me dominated by magnetic confinement. The fine structure is shifted du e to the magnetic field. The main result is that, as the magnetic fiel d increases, the effect of the subband mixing at the interfaces become s negligible and the fine structure tends to disappear at strong field s. We provide a straightforward interpretation for the mechanism under lying this transition and conjecture that it has the same origin as th e one recently observed in a different device. (C) 1996 American Insti tute of Physics.