Regensburg 2000 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 12: Poster I: Quanten Hall Effekt (1-9), II-VI Halbleiter (10-17), Epitaxie (18-23), Quantenpunkte und -dr
ähte (24-50), Photonik (51-59), Metall-Isolator Übergang (60-64), Si/Ge (65-67), Elektronentheorie (68-69), Amorphe Halbleiter, Ionen-Implantation

HL 12.30: Poster

Montag, 27. März 2000, 14:00–19:00, A

Magnetic field induced singularities in tunneling experiments through InAs quantum dots — •I. Hapke-Wurst¹, U. Zeitler¹, R.J. Haug¹, H. Frahm², A.G.M. Jansen³, and K. Pierz⁴ — ¹Inst. f. Festkörperphysik, Appelstr. 2, D-30167 Hannover — ²Inst. f. Theoretische Physik, Appelstr. 2, D-30167 Hannover — ³Grenoble High Magnetic Field Laboratory, MPIF-CNRS, F-30842 Grenoble Cedex 09 — ⁴Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig

We have performed magneto-tunneling experiments through self assembled InAs quantum dots embedded in an AlAs barrier. IV-characteristics were measured at low temperatures down to 400 mK and magnetic fields up to 28 Tesla. At zero magnetic field we observe clear current steps with a typical height of Δ I ≈ 50 pA. Applying a small magnetic field parallel to the current leads to Zeeman splitting of the steps (g=0.8). For higher magnetic fields the current steps resulting from tunneling of the emitter minority spins through the lower dot level decrease in height whereas the majority spin steps through the higher dot level develop into strongly enhanced current peaks. We interpret these features as spin dependent singularities. The slope of the peaks can be described by I ∼ (V−V_c)^−γ. We extract an exponent γ which increases for the majority spin to an extremely high value of γ = 0.5 at 28 Tesla. The experimental values are compared with theoretical calculations for magnetic field induced Fermi edge singularities in our tunneling structures.