Single-electron charging of self-assembled InAs quantum dots
  The many-particle ground state and excitations of self-assembled InAs quantum dots are investigated using far-infrared (FIR) and capacitance spectroscopy. The contributions of quantization and charging energies to the $n$--electron energy spectrum are determined. For $n = 1$, 2, we find good agreement with a parabolic model; for higher filling, the Coulomb interaction reveals itself not only in the capacitance, but also in the FIR excitations 
M. Fricke, A. Lorke, M. Haslinger and J. P. Kotthaus, G.   Medeiros-Ribeiro and P. M. Petroff