Carrier dynamics of ErAs:GaBixAs1-x using infrared pump, terahertz probe spectroscopy.

ErAs:GaBiAs is a complex physical system that offers several interesting components within the same materials, including Bi-related alloy disorder, Bi-induced localization, and ErAs-related bound and interface states. The interplay among these components leads to competing pathways for carrier relaxation. While carrier dynamics in GaBiAs and ErAs:GaAs have been studied extensively, dynamics in the composite material ErAs:GaBiAs, with both ErAs and GaBiAs components, remain largely unexplored. This dissertation investigates the carrier dynamics of ErAs:GaBixAs1−x(x = 0.053) samples containing 0 8% and 1 6% ErAs nanoparticles using infrared pump-terahertz probe spectroscopy. We excite samples with an infrared pump, with photon energies ranging from 0.48 eV to 1.09 eV, and probe the samples’ response with a terahertz (THz) pulse. By analyzing pump-induced THz transmission through the samples under varying excitation conditions, such as fluence, temperature, and ErAs nanoparticle concentration, we identify four distinct sets of transient photoconductivity dynamics driven by the excitation energy relative to the bandgap and the ErAs levels. Under above-bandgap excitation, measurements revealed that the transient photoconductivity of ErAs:GaBiAs decays rapidly within a sub-picosecond timescale due to carrier trapping by ErAs nanoparticles, followed by a slower defect-assisted recombination. Unlike rapid carrier trapping, slower recombination is strongly fluence-, ErAs nanoparticles concentration-, and temperature-dependent. Comparison of the transient photoconductivity between samples with two ErAs nanoparticle concentrations revealed systematic variations in the decay amplitude and lifetime, arising from differences in carrier mobility and the density of ErAs-related trapping and recombination centers. Experiments under near-bandgap, below-bandgap but above-ErAs, and below-bandgap and below-ErAs excitation showed a strong transient photoconductivity despite the absence of band-to-band excitation. Under these excitation conditions, the transient photoconductivity decays via a single slow recombination channel on a timescale of hundreds of picoseconds, and the mechanisms underlying this decay differ depending on the excitation energy relative to the ErAs levels. These results provide a comprehensive picture of the ultrafast carrier dynamics of ErAs:GaBiAs. Furthermore, this work establishes an experimental platform for understanding the intricate dynamics of a complex material system and opens avenue for tailoring the properties of engineered materials.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Doctoral

Grantor

Baylor University.

Year dc:date.issued

2026

Author dc:creator

• Giri, Mohan, 1993-

Advisor dc:contributor.advisor

• Hilton, David J.

• Carrier dynamics.
• Ultrafast spectroscopy.
• Pump-probe.
• Terahertz.

Statement dc:rights

• Baylor University works 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. Contact libraryquestions@baylor.edu for inquiries about permission.

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/2104/14635

OAI identifier oai:identifier

oai:baylor-ir.tdl.org:2104/14635