A single-electron memory, in which a bit of information is stored by one electron, is demonstrated at room temperature. The memory is a floating gate metal-oxide-semiconductor transistor in silicon with a channel width ( approximately 10 nanometers) smaller than the Debye screening length of a single electron and a nanoscale polysilicon dot ( approximately 7 nanometers by 7 nanometers) as the floating gate embedded between the channel and the control gate. Storing one electron on the floating gate screens the entire channel from the potential on the control gate and leads to (i) a discrete shift in the threshold voltage, (ii) a staircase relation between the charging voltage and the shift, and (iii) a self-limiting charging process. The structure and fabrication of the memory should be compatible with future ultralarge-scale integrated circuits.

We report the fabrication and characterization of lithographically defined nanoscale silicon quantum-dot transistors that operate at temperatures over 100 K and a bias higher than 0.07 V. In the tunneling regime, these transistors show strong current oscillations due to quantum confinement and single-electron charging effects. In the propagating regime, a different kind of current modulation has been observed, which is attributed to the interference between different modes of quantum waves in a cavity. Proper scaling of these transistors should lead to operation at room temperature and a bias of 0.3 V.

We have demonstrated a room-temperature silicon single-electron transistor memory that consists of ͑i͒ a narrow channel metal-oxide-semiconductor field-effect transistor with a width ͑ϳ10 nm͒ smaller than the Debye screening length of single electron; and ͑ii͒ a nanoscale polysilicon dot ͑ϳ7ϫ7 nm͒ as the floating gate embedded between the channel and the control gate. We have observed that storing one electron on the floating gate can significantly screen the channel from the potential on the control gate, leading to a discrete shift in the threshold voltage, a staircase relationship between the charging voltage and the threshold shift, and a self-limiting charging process.

Novel p-channel quantum-dot transistors were fabricated in silicon-on-insulator. Strong oscillations in the drain current as a function of the gate voltage have been observed at temperatures over 81 K and drain biases over 66 mV. The oscillations are attributed to holes tunneling through the discrete single hole energy levels in the quantum dot. Measurements show that the average energy level spacing is ϳ35 meV. Simple modeling indicates that about two thirds of the energy level spacing come from the Coulomb interaction between holes ͑i.e., hole Coulomb blockade͒ and one third from the quantum confinement effect. The realization of single hole quantum-dot transistors opens new possibilities for innovative circuits that utilize complementary pairs of quantum-dot transistors.

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