RESONANT MAGNETOTUNNELING VIA QUANTUM-CONFINED STATES

We have measured the low temperature current-voltage characteristics ( I(V)) of GaAs/AlAs resonant tunnelling diodes with sub-micron lateral dimensions. Additional peaks in I(V) are observed due to resonant tunn elling via one-dimensional quantum wire states. In the presence of a m agnetic field oriented perpendicular to the current and parallel to th e wire the peaks show a complex splitting evolving into a regular seri es at high field with up to 20 resonances. For the smallest device we are able to deduce the probability density of the lowest three bound s tates from the magnetic field dependence of the current and show that the confining potential is close to parabolic. For a magnetic field wh ich is perpendicular to both the current and the wire a much weaker de pendence on magnetic field is observed confirming the one-dimensional nature of our device. Finally, in the presence of a field oriented par allel to the current a continuous transition from electrostatic (at lo w field) to magnetic confinement (at high field) is observed.