Electron dynamics in a biased quantum well

Date of Completion

January 1997


Engineering, Electronics and Electrical|Physics, Condensed Matter




With the advancements in modern growth techniques such as MBE and MOCVD, the addition of quantum wells within semiconductor devices has expanded considerably over the past decade. For instance, quantum well infrared photodetectors (QWIPs) rely upon a series of uncoupled quantum wells to detect light by exciting a bound electron into the continuum of states above the quantum well.^ Even though the fabrication of quantum well devices has advanced considerably, a theoretical understanding of these devices has not proceeded as quickly. This is a result of modeling quantum well devices with physics that only applies with no electric field for cases with an electric field. It is the situation of a biased quantum well and the dynamics of electrons that this dissertation addresses.^ The application of an electric field perpendicular to a quantum well changes an otherwise closed system into an open system. This results in redistributing the density of states both above the conduction band offset as well as below. As the scattering of an electron via a polar optical phonon is a strong function of the location of the initial and final states, the resulting redistribution of the density of states has a large affect on the scattering rate of an electron. Furthermore, since the escape of an electron from a quantum well relies upon the location of the electron in energy within the quantum well, any change in the density of states below the band offset affects the escape rate. Also, when light is incident upon a quantum well, the absorption coefficient of the electron is a function of the final states. As the final states redistributes with an applied electric field, so will the absorption rate. It is these affects which are addressed within the contents of this dissertation. ^