RESONANT-TUNNELING QUANTUM DOTS AND WIRES - SOME RECENT PROBLEMS AND PROGRESS

Electron tunnelling through donor-related states is discussed. This tu nnelling process, which occurs well below the threshold voltage for co nventional resonant tunnelling into the two-dimensional continuum stat es of the quantum well, reveals a new type of Fermi edge singularity e ffect which arises from the Coulomb interaction between the tunnelling electron on the localized site and the Fermi sea of electrons in the emitter layer. A new means of forming laterally confined resonant tunn elling devices is also described. By studying the effect of an applied magnetic field, the additional structure that appears in the current- voltage characteristics of these devices can be unambiguously associat ed with a lateral quantum mechanical confinement effect.