Theoretical Study Of The Transport Characteristic Of Single Electron Devices

Abstract:In the practical application, the current accuracy and sensitivity determine quality of the single electron devices (SET). Therefore, it is very important to study theoretically the transport characteristic of the SETs.Firstly, we give an overview of the SETs, including the development history, the two basic structures, several kinds of devices based on silicon and their preparation technologies, as well as the applications in nano-electronics. Secondly, we analyze the basic principles, the effect of Coulomb blockade and quantum tunneling effect, of the single-electron devices in detail, and two kinds of numerical simulation methods of the single-electron device. According to the work of the mechanism of dynamic error, we give the phenomenological formulas of the tunneling resistance, the rate of motion, and the probability of finding that the number of electrons on the island for the charge-coupling-device (CCD).In chapter three, we research the influence of the temperature on the tunneling resistance and the rate of motion for the CCD. When the temperature is less than7K, the tunneling resistance increases nonlinearly with the gate voltage. With the temperature increasing, the resistance decreases, and the probabilities of the electrons going into and off the island increase. The rise of temperature makes the energy of thermal motion increase, and the effect of coulomb blockade destroyed, so the number of the electrons is unstable in the island. In a certain range, we can improve appropriately the gate voltage, and make the condition of the effect of coulomb blockade meet again.Finally, in the standard way for a master equation, we use master equation to calculate the rates of probabilities as a function of time for the variety states. We provide the method of determining the best optimization conditions by optimizing the gate voltage linearly changing with time and trying to reduce the magnitude of the error probability, the effects of the waiting time and the waiting gate voltage are discussed. Due to the strong tunneling effect, the minimum probability of error appears at in the temperature of T=7K, the value low as10-5, when the simple linear gate voltage applied. However, the lower temperature of the device, the lower error probability is after the optimization, and the minimum is about10-14. When T<7K, this voltage optimization is very effective so that error probability reduce several orders of magnitude. The lower the temperature, this effect is more obvious. However, when the temperature is reduced to2K the error probability decreases more slowly. The capacitance of the quantum dot also affected the value of the error probability, the error probability decreases with the capacitor value decreases, the lower quantum dot capacitance, the more obvious influence on the error probability. Adopted the similar optimization, the error probability is greatly reduced quantum island capacitance5aF when the error probability values as low as10-20.