Landau-Level Spectroscopy of a Two-Dimensional Electron System by Tunneling through a Quantum Dot

A single InAs self-assembled quantum dot is incorporated in the barrier of a tunnel diode and used as a spectroscopic probe of an adjacent two-dimensional electron system from the Fermi energy to the subband edge. We obtain quantitative information about the energy dependence of the quasiparticle lifetime. For magnetic field $B$, applied parallel to the current, we observe peaks in the current-voltage characteristics $I\left(V\right)$ corresponding to the formation of Landau levels. Close to filling factor $\nu =1\mathrm{}$ we observe directly the exchange enhancement of the Landé $g$ factor.