Ambipolar nonvolatile memory based on a quantum-dot transistor with a nanoscale floating gate

Using only solution processing methods, we developed ambipolar quantum-dot (QD) transistor floating-gate memory (FGM) that uses Au nanoparticles as a floating gate. Because of the bipolarity of the active channel of PbSe QDs, the memory could easily trap holes or electrons in the floating gate by programming/erasing (P/E) operations, which could shift the threshold voltage both up and down. As a result, the memory exhibited good programmable memory characteristics: a large memory window (ΔV_th ∼ 15 V) and a long retention time (>10⁵s). The magnitude of ΔV_th depended on both P/E voltages and the bias voltage (V_DS): ΔV_th was a cubic function to V_P/E and linearly depended on V_DS. Therefore, this FGM based on a QD transistor is a promising alternative to its inorganic counterparts owing to its advantages of bipolarity, high mobility, low cost, and large-area production.