Multiple-Step Electron Charging in Silicon-Quantum-Dot Floating Gate Metal-Oxide-Semiconductor Memories

Abstract

The drain current versus gate voltage characteristics of metal-oxide-semiconductor field-effect-transistors (MOSFETs) with silicon-quantum-dots (Si-QDs) layer floating gate have shown clear current bumps arising from the multiple-step charging of the QDs floating gate at room temperature. The transient drain current characteristics at constant positive gate biases indicate that the electron charging of the QDs floating gate proceeds stepwise, suggesting that the redistribution of injected electrons in the QDs floating gate proceeds as a result of the Coulomb interaction among charged QDs. It is suggested that not only the charged states of individual QDs but also the charged states of neighboring QDs are crucial factors for progressive electron charging.