Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session M34: Photodetectors and Optical Emitters
8:00 AM–10:48 AM,
Wednesday, March 8, 2023
Room: Room 226/227
Sponsoring
Unit:
FIAP
Chair: Jay Mathews, University of Dayton
Abstract: M34.00011 : Coherent Acoustic Phonon Oscillations in Ge Using Pump-Probe Time-Resolved Spectroscopic Ellipsometry*
10:00 AM–10:12 AM
Presenter:
Carlos A Armenta
(New Mexico State University)
Authors:
Carlos A Armenta
(New Mexico State University)
Martin Zahradnik
(ELI Beamlines)
Carola Emminger
(Leipzig University)
Shilry Espinoza
(ELI Beamlines)
Mateusz Rebarz
(ELI Beamlines)
Jakob Andreasson
(ELI Beamlines)
Stefan Zollner
(New Mexico State University)
Collaboration:
NMSU, ELI Beamlines, Semiconductor Physics Group Leipzig University, Department of Physics Humboldt University of Berlin
The present work aims to describe the relationship between CAP oscillations and charge carrier density, as well as surface orientation dependence via femtosecond pump-probe ellipsometry of Ge. Photoexcitation is induced by 800 nm laser pump pulses at different intensities, generating a strain pulse that travels normal to the surface within the ∼200 nm penetration depth in the semiconductor. Measurements in Ge at (100), (110), and (111) orientations and charge carrier concentrations ranging from ∼7.5×1020 cm-3 to ∼3.5×1021 cm-3 were performed. The behavior of these oscillations is characterized by analyzing the changes in the pseudo-DF of Ge as a function of the delay time between the pump and probe pulse. Analyzing the E1 and E1+Δ1 critical points (CP) and the variation of their parameters (energy, broadening, amplitude, and phase) with delay time, the behavior of phonon oscillations can be studied.
In order to determine these parameters, second derivatives of the pseudo-DF were calculated using a linear filter technique based on extended Gauss (EG) functions. The periods of these oscillations are deduced by tracking the energy of these CPs as a function of time.
*Air Force Office of Scientific Research
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