Ambipolar Quantum-Dot-Based Low-Voltage Nonvolatile Memory with Double Floating Gates

Considerable research efforts have been devoted to promoting memory performance, especially the memory window and retention time. In this work, we develop an innovative field-effect-transistor memory with graphene oxide (GO)/gold nanoparticles (Au NPs) as double floating gates (DFG) and PbS quantum dots (QDs) as the semiconductor layer. QDs can provide both electrons and holes in the channel, which offers a chance for the floating gates to trap both of them to achieve bidirectional threshold voltage shifts after programming and erasing operations. Due to the DFG structure covering the GO sheets on the Au NP monolayer, the enhanced memory window (similar to 2.72 V at a programming/erasing voltage of +/- 10 V) can be attributed to more charge carriers being trapped in the floating gates. More importantly, because of the different energy levels between GO and Au NPs, the DFG construction brings about an energy barrier that prevents the trapped charges from leaking back to the channel, so that the retention capability is significantly improved. The outstanding memory performance will give the QD-based DFG memory great potential to have its own place in the flash memory market.