Highly Sensitive Switchable Heterojunction Photodiode Based on Epitaxial Bi₂FeCrO₆ Multiferroic Thin Films

Area of Science:

• Materials Science
• Condensed Matter Physics
• Device Engineering

Background:

• Perovskite multiferroic oxides possess tunable ferroelectric polarization, suitable band gaps (<3.0 eV), and high absorption coefficients.
• These properties make them promising for sensitive and switchable photodiode applications.
• Existing photodiodes lack efficient switching capabilities and high sensitivity.

Purpose of the Study:

• To fabricate and characterize a high-speed switchable photodiode utilizing a multiferroic Bi2FeCrO6 (BFCO)/SrRuO3 (SRO) heterojunction.
• To investigate the charge carrier transport and ultrafast charge transfer dynamics within the BFCO/SRO interface.
• To demonstrate the switchable behavior of the photodiode upon reversal of electric polarization.

Main Methods:

• Pulsed laser deposition was employed to fabricate the BFCO/SRO-layered heterojunction.
• Device performance was evaluated by measuring the ideality factor and response time.
• Time-resolved photoluminescence decay spectroscopy was used to study charge transfer dynamics.

Main Results:

• The fabricated photodiode exhibited a fast response time of 68 ms and a large ideality factor (n ≈ 5.0).
• Ultrafast charge transfer with a lifetime of approximately 6.4 ns was observed in the BFCO/SRO heteroepitaxial structures.
• The photodiode demonstrated switchable directionality upon external voltage pulse-induced polarization reversal.
• A responsivity of 0.38 mA W⁻¹ at 500 nm and zero bias was achieved, the highest reported for ferroelectric thin film photodiodes.

Conclusions:

• The Bi2FeCrO6/SrRuO3 heterojunction photodiode shows significant potential for high-performance optical sensing.
• Multiferroic oxides are viable materials for developing highly sensitive and switchable photodiodes.
• This research paves the way for advanced applications in optical switching and detection.