Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 11: Quantum dots and wires: Transport properties I
HL 11.4: Vortrag
Montag, 26. März 2007, 15:30–15:45, H15
Charge detection for ballistic electron spectroscopy — •Frank Hohls1,2, Michael Pepper2, Jonathan P. Griffiths2, Geb A.C. Jones2, and David A. Ritchie2 — 1Institut für Festkörperphysik, Universität Hannover — 2Cavendish Laboratory, University of Cambridge, UK
We have shown that a quantum dot can be used for the direct energy resolved detection of ballistic electrons [1]. This allows us to measure the energy and angle distribution of ballistic electrons injected by e.g. a quantum wire or another dot. In the original scheme the usable energy range was limited by the presence of excited states to a few 100 µeV.
Here we will present a modified detector design that allows us to extend the energy range to at least 1 meV. We largely increase the excitation energy by using a small quantum dot on the transition between 0 and 1 electron. The readout is performed by a nearby quantum point contact utilised as charge detector. The average charge on the dot is a direct function of the density of electrons attempting to enter the dot at its resonance energy.
We apply this scheme to assess the energy spectrum of non-equilibrium ballistic electrons that are injected by a quantum point contact and have traversed a few micrometer through a two-dimensional electron system. We discuss the energy distribution and scattering mechanisms.
[1] F. Hohls et al., Appl. Phys. Lett. 89, 212103 (2006).