Fine structure in magnetospectrum of vertical quantum dot

The electronic transport properties of a gated vertical quantum dot fabricated of an asymmetrical InGaAs/AlGaAs double-barrier resonant tunneling heterostructure are studied experimentally. At a temperature of 15 mK, a series of small current peaks are observed far below the voltage of a main resonance peak. The voltage position of these peaks appeared to be strongly dependent on the presence of magnetic field oriented perpendicular to the plane of the barriers. The occurrence of the peaks is attributed to tunneling mechanisms involving inter-Landau-level resonant tunneling, longitudinal-optical (LO)-phonon-assisted tunneling and to electrostatic effects such as Coulomb blockade.