Wavelength-selective bipolar photoresponse in CVD-grown β-Bi₂O₃ flakes for multi-logic functionality.

Area of Science:

• Materials Science
• Optoelectronics
• Solid State Physics

Background:

• Optoelectronic logic devices are crucial for high-speed, energy-efficient computing.
• Bismuth oxide (β-Bi2O3) is a promising material for next-generation photonic systems.
• Controlling photodetector behavior is key for advanced logic operations.

Purpose of the Study:

• To achieve controlled growth of β-Bi2O3 via chemical vapor deposition (CVD).
• To investigate the unique bipolar photoconductive effects in β-Bi2O3.
• To demonstrate wavelength-controlled optoelectronic logic gates using β-Bi2O3.

Main Methods:

• Systematic tuning of growth parameters for β-Bi2O3 using CVD.
• Characterization of photodetector response under varying illumination wavelengths.
• Fabrication and testing of logic gates by modulating excitation wavelength.

Main Results:

• Observed positive photoconductivity under above-bandgap illumination and negative photoconductivity at longer wavelengths.
• Demonstrated that bipolar photoresponse is governed by carrier dynamics, defect states, and electron-phonon scattering.
• Successfully realized all seven fundamental logic gates by solely modulating illumination wavelength.

Conclusions:

• The coexistence of positive and negative photoconductivity in β-Bi2O3 enables wavelength-controlled logic operations.
• This approach offers a compact and reconfigurable method for in-sensor computing and photonic logic.
• Highlights the interplay between photon energy, defect states, and electron-phonon interactions in β-Bi2O3.