Semiconductor single-electron transistors and memories.

摘要

Single electron effects are manifested in semiconductor nanostructures as a result of the Coulomb interaction and quantum confinement of the electronic charges. This thesis explores two applications of the single electron effects in nanoscale semiconductor devices, namely, the single-electron transistor and the single-electron memory.; We have investigated the charge transport in single-electron and single-hole quantum dot transistors that have a channel consisting of a silicon dot separated from the source and the drain by two constrictions. We have also fabricated quantum dot transistors in GaAs/AlGaAs heterostructure to assist our study of the Coulomb blockade transport effect. More importantly, we have been able to achieve silicon quantum dot size beyond the limitation of electron beam lithography, and have observed Coulomb blockade of single charge tunneling effect above liquid nitrogen temperature.; By using a structure that has a nanoscale polysilicon-dot floating gate stacked on a narrow silicon channel, we have demonstrated the first room temperature single-electron MOS memory in crystalline silicon. We have observed quantized threshold voltage shift, quantized charging voltage, and a self-limited charging process.; By combining the floating-gate concept with the quantum dot transistor, we have designed a new stacked quantum dot transistor. We observed that charging the floating gate with electrons not only shifted the threshold voltage of the transistor, but also significantly enhanced the conductance oscillations in the quantum dot channel. Such an enhancement is attributed to the reduction of the effective quantum dot size, which leads to an increase in the energy level separation.; In searching for the technology that would allow the fabrication of nanoelectronic devices in a cost effective and time efficient way, we have applied the newly developed nanoimprint lithography for the first time to fabricate nanoscale silicon field effect transistors, and have examined its effect on the device performance. This investigation represents one step forward in demonstrating that nanoimprint lithography could become a viable nanofabrication technology.