The negative differential capacitance (NDC) effect is observed on a titanium-oxide-silicon structure, formed on n-type silicon with embedded germanium quantum dots (QDs). The Ge QDs were grown by an Sb-mediated technique. The NDC effect was observed for temperatures below 200 K. We found that approximately six to eight electrons can be trapped in the valence band states of Ge QDs. We explain the NDC effect in terms of the emission of electrons from valence band states in the very narrow QD layer under reverse bias.
Keywords: 10.06; 10.10; 20.11; CV; Ge quantum dots; Ge quantum pyramids; metal oxide semiconductor; negative differential capacitance.