The nonlinear optical response of low-temperature (LT) grown GaAs were studied
using four-wave mixing techniques. Through measurements of the four-wave mixing
response as a function of pulse delay and photon energy, a strong optical response
was identi ed associated with the fundamental band gap exciton. These experiments
therefore demonstrated the importance of the exciton in understanding the ultrafast
nonlinear optical response of LT-GaAs despite the absence of any evidence of the
exciton in past linear absorption studies in this material. Measurement of the fourwave
mixing response as a function of pulse delay and the polarization states of the
two excitation pulses shows that the dominant contribution to the exciton signal is
tied to excitation-induced dephasing. Four-wave mixing experiments in which the
sample is exposed to an additional laser pulse indicate that the exciton signal may be
strongly diminished due to a combination of screening and a reduction in the total
dephasing time. The short temporal duration of the above e ect provides evidence
of an ultrashort (< 100 fs) electron trapping time in this system tied to arsenic
related defects introduced during low-temperature growth. These ndings are of
importance to the understanding of the optical properties of LT-GaAs and will aid
in the development of optoelectronic devices using this material system.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/42700 |
| Date | 30 October 2013 |
| Creators | Webber, Daniel |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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