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Dynamics of Optically-Generated Carriers in Si (100) and Si (111) Substrate-Grown GaAs/AlGaAs Core-Shell Nanowires
Ramon Delos Santos1, Jasher John Ibañes, Maria Herminia Balgos
1National Institute of Physics, University of the Philippines, Diliman, Quezon City, Philippines, rdelossantos@nip.upd.edu.ph.
Nanoscale Research Letters
|August 22, 2015
Summary
Gallium arsenide/aluminum gallium arsenide core-shell nanowires grown on silicon substrates exhibit distinct carrier dynamics. Si (111) substrates enhance photoluminescence, while terahertz emission is independent of carrier recombination lifetime.
Area of Science:
- Materials Science
- Nanotechnology
- Semiconductor Physics
Background:
- Gallium arsenide/aluminum gallium arsenide (GaAs/AlGaAs) core-shell nanowires (CSNWs) are promising for optoelectronic applications.
- Understanding carrier dynamics in these nanostructures is crucial for device optimization.
Purpose of the Study:
- To investigate the growth and optical properties of GaAs/AlGaAs CSNWs on different silicon substrates.
- To analyze carrier dynamics, including recombination and transport, using time-resolved techniques.
- To explore the generation of terahertz (THz) radiation from these CSNWs.
Main Methods:
- Molecular beam epitaxy (MBE) for CSNW growth on gold nanoparticle-activated Si (100) and Si (111) substrates.
- Room temperature-photoluminescence (RT-PL) spectroscopy to assess bandgap emission and intensity.
- Time-resolved photoluminescence (TRPL) to measure carrier recombination lifetimes.
- Ultrafast photoexcitation and terahertz (THz) emission measurements to probe carrier transport.
Main Results:
- GaAs/AlGaAs CSNWs exhibited bulk-like GaAs and AlGaAs emission peaks.
- Higher PL intensity was observed for CSNWs on Si (111) due to improved shell passivation.
- Carrier recombination lifetimes were 333 ps on Si (100) and 500 ps on Si (111).
- THz emission intensity and bandwidth showed negligible differences between substrates, independent of recombination lifetime.
- Fabry-Perot modes were observed in the THz spectrum for CSNWs on Si (111) due to substrate reflections.
Conclusions:
- The substrate type significantly influences the optical properties and carrier recombination in GaAs/AlGaAs CSNWs.
- Surface passivation by the AlGaAs shell is critical for enhanced photoluminescence on Si (111).
- Terahertz emission is governed by mechanisms distinct from carrier recombination lifetime in this configuration.
- The findings provide insights into the fundamental properties of CSNWs for potential THz device applications.
