Defect Engineering in β-Bi₂SeO₅/Bi₂O₂Se Heterostructures for High-Resolution Phototransistor Arrays.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• The β-Bi₂SeO₅/Bi₂O₂Se heterojunction shows promise for electronic devices, analogous to SiO₂/Si.
• Photodetection in Bi₂O₂Se is limited by surface selenium vacancies, causing low photocurrent and instability.

Purpose of the Study:

• To explore the potential of the β-Bi₂SeO₅/Bi₂O₂Se architecture for improving optoelectronic properties of Bi₂O₂Se.
• To address surface vacancy limitations in Bi₂O₂Se for enhanced photodetection performance.

Main Methods:

• Fabrication of a defect-engineered β-Bi₂SeO₅/Bi₂O₂Se heterojunction using UV-assisted oxidation.
• Characterization using first-principles calculations to confirm band alignment and carrier dissociation.
• Fabrication of top-gated phototransistors and a high-resolution phototransistor array using thermal scanning probe lithography.

Main Results:

• The heterostructure effectively suppresses surface vacancies, providing surface passivation and photoactive charge separation.
• Achieved significantly enhanced optoelectronic performance: responsivity (1.2 × 10⁴ A W^-1), detectivity (1.5 × 10¹³ Jones), and on/off ratio (2.3 × 10⁶).
• Demonstrated imaging capabilities with a high-resolution β-Bi₂SeO₅/Bi₂O₂Se phototransistor array (pixel pitch = 6.5 µm).

Conclusions:

• The defect-engineered β-Bi₂SeO₅/Bi₂O₂Se heterojunction offers a promising strategy for high-performance optoelectronic devices.
• The developed UV-assisted oxidation and patterning techniques enable in situ large-area growth and high-resolution device fabrication.
• β-Bi₂SeO₅/Bi₂O₂Se is a viable platform for advanced photodetectors and imaging applications.