COMPETING CHANNELS IN SINGLE-ELECTRON TUNNELING THROUGH A QUANTUM-DOT

Coulomb blockade effects axe investigated in lateral transport through a quantum dot defined in a two-dimensional electron gas. Tunneling th rough excited states of the quantum dot is observed for various tunnel ing barriers. It is shown that transport occurring via transitions bet ween ground states with different numbers of electrons can be suppress ed by the occupation of excited states. Measurements in a magnetic fie ld parallel to the current give evidence for tunneling processes invol ving states with different spin.