Subband mixing in resonant magnetotunneling through double-barrier semiconductor nanostructures

We investigate subband mixing in the magnetotunneling of an electron through 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-dimensional-one-dimensional tunneling process leads to a transition from a low-field regime dominated by lateral confinement to a high-field regime dominated by magnetic confinement. The fine structure is shifted due to the magnetic field. The main result is that, as the magnetic field increases, the effect of the subband mixing at the interfaces becomes negligible and the fine structure tends to disappear at strong fields. We provide a straightforward interpretation for the mechanism underlying this transition and conjecture that it has the same origin as the one recently observed in a different device. (C) 1996 American Institute of Physics.