Non-degenerate fs pump-probe study on InGaN with multi-wavelength second-harmonic generation

Area of Science:

• Solid State Physics
• Materials Science
• Ultrafast Spectroscopy

Background:

• Understanding ultrafast carrier dynamics in Indium Gallium Nitride (InGaN) is crucial for optoelectronic device performance.
• InGaN materials exhibit unique properties due to indium-rich nano-clusters and compositional fluctuations.
• Previous studies often lacked the resolution to probe carrier relaxation mechanisms at femtosecond timescales.

Purpose of the Study:

• To investigate the ultrafast carrier dynamics in InGaN thin films.
• To elucidate the mechanisms of carrier relaxation, including local and global thermalization.
• To utilize tunable UV-visible pump-probe spectroscopy with multiwavelength second-harmonic generation (SHG).

Main Methods:

• Implementation of non-degenerate femtosecond (fs) pump-probe experiments in the UV-visible range.
• Generation of multiwavelength second-harmonic generation (SHG) pulses from a 10 fs Ti:sapphire laser using two beta-barium borate crystals.
• Characterization of SHG pulse widths (~150 fs) via cross-correlation with a two-photon absorption detector.

Main Results:

• Successful application of the developed technique to probe InGaN thin films.
• Observation of carrier relaxation via scattering-induced local thermalization (<1 ps).
• Identification of carrier-transport-dominating global thermalization occurring over several picoseconds.

Conclusions:

• The study demonstrates a robust method for investigating ultrafast carrier dynamics in InGaN.
• The observed relaxation pathways provide insights into carrier behavior in nanostructured InGaN.
• Findings contribute to the fundamental understanding of InGaN properties for advanced applications.