The Study On The Resonant Tunneling And Lifetime Of Resonant State In A Spherical Quantum Dot

The transport properties of a single electron in low dimensional semiconductor structure have been intensively concerned in recent years. These properties are not only significantly basic theoretical physical problem but also of important application in future. In this paper, we have made a detail investigation on electronic resonant-tunneling phenomena and lifetime of resonant state through a spherical quantum dot structure which have great potential applications in future devices.The main purposes of this thesis are:(1) We study the resonant-tunneling phenomena of electron in the spherical quantum dot structure consisting of GaAs/InAs. We calculated transmission probability using a transfer matrix technique in the framework of effective mass approximation. In the spherical quantum dot, the electron is confined both laterally and vertically; we separate the motion in the vertical and lateral directions within the adiabatic approximation. We found that the smaller radius of the quantum dot lead significantly to a shift of resonant peaks toward the high-energy region, and causes the broadening of the resonant peaks and the reduction of the peak-to-valley ratio in transmission spectrum. Meanwhile, our results show that the resonant peaks don't move with changing the thickness of slice (where we have divided the spherical quantum dot into slices along axis z ).(2) We calculated the lifetime of resonant state using the time evolution of the electron wave packet in the spherical quantum dot. The lifetime is related to the energy width of the resonant level due to the uncertainty principle. These values of lifetime coincide very well with those obtained from simulation of the wave packet. The lifetime of resonant state is studied to estimate the limit to operation speed of resonant tunneling devices. We hope our calculation can help to design optimal resonant-tunneling systems in further experiments.