Terahertz quantum cascade structures using step wells and longitudinal optical-phonon scattering

View/ Open
Author
Freeman, Will
Date
2009-06Advisor
Karunasiri, Gamani
Metadata
Show full item recordAbstract
Electron transport properties of terahertz (THz) longitudinal optical (LO)-phonon quantum cascade (QC) structures were modeled, in order to investigate high gain quantum cascade laser (QCL) structures. A new structure, a step well QC structure, was proposed. Under such an arrangement, there are three main energy levels within the step well, where the transition from the upper state to the middle state is at the THz radiative spacing and the transition from the middle state to the lower state is at or near the LOphonon energy (~ 36 meV in GaAs). Because of the inherent difficulties in using rate equations for this type of transport analysis, a Monte Carlo simulation was developed. Step well injectors were modeled and shown to be capable of high injection efficiencies (~ 90%), higher than previously obtained. Comparisons to conventional square well LOphonon structures are made, including a Monte Carlo analysis of a high power THz QCL. Interface roughness scattering was shown to be significant only for roughness greater than approximately one monolayer. It was found that step well structures are capable of high gains and injection efficiencies, with comparable characteristics to other square well designs, but do have increased scattering from the upper state to the lower states.
Description
Approved for public release, distribution unlimited
Collections
Related items
Showing items related by title, author, creator and subject.
-
A systems effectiveness model for an alternative structured complex system
Keim, Clarence Howard (Monterey, California. U.S. Naval Postgraduate School, 1968-06);A complex system envisioned can accomplish a given mission with the aid of any one of several alternative structures. Each of these alternative structures (subsystems) , although capable of mission accomplishment, ... -
High temperature x-ray studies of a Cu-Be alloy.
McHugh, William M. (Monterey, California: U.S. Naval Postgraduate School, 1965);The Debye-Scherrer method has been used to study the sequence of precipitation structures in a two percent beryllium-copper alloy. A special x-ray camera fitted with a furnace was used to follow the age-hardening process ... -
Identification and evaluation of organizational structures and measures for analysis of Joint Task Forces
Olechnowicz, Stephen M. (Monterey California. Naval Postgraduate School, 1999-12);Joint Task Forces (JTF) operate in a variety of missions and uncertain environments. The architectures of these organizations must be capable of adapting to changes in the mission, the environment, or the organization ...