Electron tunneling dynamics in engineered semiconductor nanostructures and applications to efficient solar cells

This thesis investigates the electron tunneling dynamics in engineered semiconductor nanostructures in the presence of electron-hole and electron-phonon interactions for device and solar applications. The temporal dynamics of a traveling electron wave packet in a double barrier structure was calculated as a function of wave packet's central incident energy by calculating the charge build-up inside the quantum well. As time passes 40 fs features associated with resonance started to develop. The electron tunneling dynamics problem were also extended to include electron-hole interaction on the coherent oscillation of a photoexcited electron wave packet in a double quantum well structure. It is shown both in energy and time domains that the electron hole interaction affect the electron wave packet's oscillation period by as much as 15%. This method was extended to include the presence of electron-plane wave and electron-localized LO phonon interactions on the dynamics of electron tunneling. It was shown that the tunneling current and charge build-up decreases in the presence of these LO phonon modes while the tunneling times are not affected.; One of the key aspects of this thesis is the use of electron resonant tunneling in MQW based solar cell structures for the purpose of high energy conversion efficiency. By incorporating tunneling through a MQW structure with different quantum well sizes in a p-i-n structure, higher efficiency was achieved by eliminating intrinsic losses associated with the single band gap solar cell structures. The effect of MQW solar cell structures made with small quantum well material band-gap such as that of InAs in InAs/GaInAs structures and a large band-gap as that of GaAs in GaAs/AlGaAs were presented.