Analysis of the electron transport properties in quantum cascade lasers

Recently, the operating frequency range of quantum-cascade lasers (QCLs) has been extended from the mid-infrared to the far-infrared beow the Reststrahlen band (THz frequencies). Especially for THz QCLs, a detailed understanding of the dynamics of the electron transport is essential in order to extend their operation to longer wavelengths and higher temperatures. Compared to mid-infrared structures, the small subband separations in THz QCLs lead to LO-phonon scattering rates that are highly temperature sensitive and increases the importance of scattering processes which favor small transition energies, such as electron-electron (e-e), electron-impurity (e-imp)and electron-interface roughness scattering. This thesis details the development and calculation results for different models for the electron transport in THz QCLs. Using a semi-classical Monte Carlo simulation, including e-e and e-LO-phonon scattering as well as e-imp scattering, the current density, population density and gain in two THz QCLs were investigated. We find that the inclusion of e-imp scattering in the calculations is crucial when modeling the intersubband transport dynamics in these devices. However, the calculated gain and current density exceed the measured values due to the absence of wavefunction localization and dephasing scattering in this model.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Callebaut, Hans, 1975-

Advisor dc:contributor.advisor

• Qing Hu.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/37893

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/37893