Figure 5
From: Si solid-state quantum dot-based materials for tandem solar cells
Schematic illustration of "modified modulation" doping. (a) QDs dispersed in a stoichiometric SiO2 matrix - dopant atoms cannot be ionised as they create very deep levels. (b) QDs surrounded by an amorphous sub-oxide region between regions of full stoichiometric barrier material - dopant atom levels are shallow enough to be ionised at room temperature and 'modulation' dope the QDs.