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-dimensi onal electron system from the Fermi energy to the subband edge. We obtain q uantitative information about the energy dependence of the quasiparticle li fetime. For magnetic field B, applied parallel to the current, we observe p eaks in the current-voltage characteristics I(V) corresponding to the forma tion of Landau levels. Close to filling factor v = 1 we observe directly th e exchange enhancement of the Lande g factor.