研究目的
Investigating the carrier dynamics in GaAlAs photocathodes using femtosecond pump-probe spectroscopy to compare with GaAs photocathodes and understand the effects of Al element on photoemission properties.
研究成果
GaAlAs photocathodes exhibit slower initial relaxation processes compared to GaAs after 22 ps delay, attributed to better lattice match and interface recombination, with Al addition enabling adjustable spectral response ranges for blue and green light applications, offering a method to improve photocathode performance.
研究不足
The study is limited to specific Al content (0.5) in GaAlAs and may not generalize to other compositions; measurements were conducted at room temperature, potentially overlooking temperature-dependent effects; the femtosecond technique provides microsecond insights but may not capture longer-term dynamics.
1：Experimental Design and Method Selection:
Femtosecond pump-probe spectroscopy was employed to measure carrier dynamics, utilizing a two-pulse correlation method to study transient reflectance changes.
2：Sample Selection and Data Sources:
High-grade n-GaAs substrates with GaAs and GaAlAs epitaxial layers grown by MOCVD epitaxial technology were used; samples had exponential doping in the emission layer with Al content of
3：5 for GaAlAs. List of Experimental Equipment and Materials:
Femtosecond laser system for pump and probe beams, MOCVD equipment for sample growth, and measurement setup for reflectance and quantum efficiency.
4：Experimental Procedures and Operational Workflow:
Laser pulses excited the photocathode surfaces, and transient reflectance spectra were measured at room temperature with perpendicular polarization of beams; data were collected over delay times to observe relaxation processes.
5：Data Analysis Methods:
Quantum efficiency and absorption coefficient curves were fitted using specific formulas; transient reflectance data were normalized and analyzed to derive carrier dynamics.
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