Valence band diagram with the involved hole transitions in the QDIP. With delta-doping planes for (a) zero bias and (b) Ub ≠ 0. The closed circles show the states occupied with a hole. The arrows indicate the hole flow.
Yakimov et al. Nanoscale Research Letters 2012 7:494 doi:10.1186/1556-276X-7-494