  We report on capacitance-voltage spectroscopy of self-assembled InAs quantum
dots under constant illumination. Besides the electronic and excitonic charging
peaks in the spectrum reported earlier, we find additional resonances
associated with nonequilibrium state tunneling unseen in C(V) measurements
before. We derive a master-equation based model to assign the corresponding
quantum state tunneling to the observed peaks. C(V) spectroscopy in a magnetic
field is used to verify the model-assigned nonequilibrium peaks. The model is
able to quantitatively address various experimental findings in C(V)
spectroscopy of quantum dots such as the frequency and illumination dependent
peak height, a thermal shift of the tunneling resonances and the occurrence of
the additional nonequilibrium peaks.
