Berlin 2008 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 31: Poster II

HL 31.18: Poster

Dienstag, 26. Februar 2008, 16:30–19:00, Poster D

Magnetotransport studies of tunneling mechanisms in vertical quantum dot — •Oleksiy B. Agafonov¹, Tomohiro Kita², Hideo Ohno², and Rolf J. Haug¹ — ¹Institut für Festkörperphysik, Universität Hannover, Appelstraße 2, D-30167 Hannover — ²Semiconductor Spintronics Project, ERATO, JST, Japan and LNS RIEC, Tohoku University, Japan

The electronic properties of a vertical quantum dot fabricated of an asymmetrical InGaAs/AlGaAs double-barrier resonant tunneling heterostructure are investigated using magnetotunneling spectroscopy. The magnetic field is oriented perpendicular to the plane of the tunnel barriers. At a temperature of 15 mK we have observed a series of small current peaks in the vicinity of a resonance peak corresponding to the tunneling over the ground state in the quantum well. The voltage positions of some current peaks are strongly dependent on the applied magnetic field and yield straight lines of a various slope, if represented versus the strength of the magnetic field. The appearance of these lines is related to the tunneling of electrons between the Landau levels in the source electrode and the quantum dot in the presence of the external magnetic field. The voltage positions of several other current peaks show a weaker field dependence. A part of these peaks are caused by the longitudinal optical phonon-assisted tunneling process. The origin of the other peaks is related to electrostatic effects (charging effects and Coulomb blockade). The presence of Coulomb blockade in this sample is confirmed through the observation of characteristic Coulomb-diamond pattern.