Atomic-like properties of semiconductor quantum dots

We use a gated submicron double-barrier resonant tunneling structure to study transport properties of a semiconductor quantum dot containing a tunable number of electrons starting from zero. At zero magnetic field the addition energy has large maxima for special numbers of electrons in the dot, reflecting a shell structure of electronic states in a circular dot with a harmonic lateral potential. As a function of magnetic field, current peaks evolve in pairs. This arises from the antiparallel filling of spin-degenerate states. Close to zero magnetic field, however, this pairing is rearranged to favour the filling of states with parallel spins in line with Hund's rule. These observations demonstrate that the electronic spectrum for our quantum dots is analogous to that of real atoms. When the dot has asymmetry in the lateral shape, the addition energy spectrum is readily modified reflecting the disruption of the shell structure.