Ultrafast Spectroscopy and Red Emission from β-Ga2O 3/β-Ga 2S 3 Nanowires

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Gallium oxide (β-Ga2O3) is a wide-bandgap semiconductor with potential applications in electronics and optoelectronics.
• Understanding carrier dynamics is crucial for optimizing semiconductor device performance.
• Sulfurization offers a route to modify the optoelectronic properties of β-Ga2O3.

Purpose of the Study:

• To investigate the carrier dynamics in β-Ga2O3 nanowires during conversion to β-Ga2O3/Ga2S3.
• To analyze the changes in optical emission and absorption properties after sulfurization.
• To elucidate the role of mid-gap states in the modified material.

Main Methods:

• Ultrafast pump-probe spectroscopy
• Transient photoluminescence spectroscopy
• Differential absorption spectroscopy
• High-temperature H2S processing of β-Ga2O3 nanowires

Main Results:

• Initial β-Ga2O3 nanowires showed blue emission (2.4 ns lifetime).
• Processing at 500-600 °C in H2S led to suppressed blue emission and new red emission (680 nm, 19 μs lifetime).
• Differential absorption revealed state filling below the conduction band before sulfurization, transitioning to dominant free carrier absorption in β-Ga2O3/Ga2S3 due to mid-gap state excitation.

Conclusions:

• Sulfurization of β-Ga2O3 nanowires significantly alters their optical properties and carrier dynamics.
• The observed red emission and long lifetime in β-Ga2O3/Ga2S3 are linked to carrier excitation from mid-gap states.
• Free carrier absorption becomes dominant in the sulfurized material, indicating changes in charge carrier behavior.