Researchers from the the Institute of Metal Research (IMR) of the Chinese Academy of Sciences have developed a new ferroelectric ultraviolet photodetector material that overcomes the long-standing performance limitations of conventional photodetectors.

This breakthrough, published in Nature Communications, promises to enable next-generation optical detection with ultra-fast speed, high sensitivity, and low noise across a wide range of applications.

Photodetectors convert light signals into electrical currents and are fundamental to modern optoelectronics. They are essential for technologies such as high-speed optical communications, environmental monitoring, and space exploration. However, creating a material that possesses all three of these qualities has been a significant challenge.

Ferroelectric materials have long been considered promising candidates because their spontaneous internal electric fields efficiently separate photo-generated electron-hole pairs, which is a critical step in photodetection. In practice, however, the performance of most ferroelectric-based detectors is severely limited by high-density domains with varying polarization directions. These domain walls can scatter and trap charge carriers, drastically slowing down the device's response time.

To address this issue, the researchers designed and synthesized a high-quality thin film of a novel magnetoplumbite-type compound, SrAl₁₁₋δTiO₁₉ (SATO). Using advanced aberration-corrected transmission electron microscope, they discovered that The SATO film possesses a unique structure with polarization along the c-axis, exhibiting the potential for single-domain ferroelectrics.

Ferroelectric performance tests showed that the remnant polarization of SATO film reaches 7.8 μC/cm² and the polarization retention exceeds 500 hours. Optoelectronic performance measurements reveal that the SATO photodetector exhibits excellent performance with a response wavelength of 330 nm, a responsivity of 860 mA/W, a detectivity of 1.63 × 10¹³ Jones, a switching ratio of 1.9 × 10⁴, and an ultrafast rise/fall response speed of 6.8 ns/17.7 ns. These results are nearly ten thousand times faster than those of conventional ferroelectric photodetectors, shattering the previous performance ceiling.

By solving the intrinsic problem of domain-wall scattering, the SATO material unlocks the full potential of ferroelectrics for high-performance optoelectronics. It paves the way for a new generation of ultrafast, highly sensitive detectors vital for real-time high-precision applications in communication, sensing, and scientific exploration.

Microstructure of AlN and SATO thin films. (a, b) Bright-field transmission electron microscopy (TEM) image and selected area electron diffraction (SAED) pattern of the AlN/STO cross-sectional sample. (c, d) Bright-field TEM image and SAED pattern of the SATO/STO cross-sectional sample. No obvious ferroelectric domain walls were observed in the SATO thin film, indicating its single-domain characteristic. Scale bars: 20 nm. (Image by IMR)

Atomic structure of the SATO thin film along three low-index zone axes. (a-c) High-angle annular dark-field (HAADF) and (d-f) annular bright-field (ABF) scanning transmission electron microscopy (STEM) images viewed along the [1120], [1100], and [0001] zone axes, respectively. The SATO structure consists of alternating rock-salt blocks (R) and spinel blocks (S) stacked along the c-axis. Scale bar: one nm. (Image by IMR)

Atomic-scale EDS elemental mapping of the SATO thin film. (a) HAADF-STEM image of the SATO thin film. (b-e) Elemental distribution maps of Sr, Al, Ti, and O. (f) Overlay image of Sr, Ti, and Al elemental signals. Ti atoms partially substitute for Al atoms at the 4f1 Wyckoff position. Scale bar: 5 Å. (Image by IMR)

Ferroelectric properties of the SATO thin film. (a-c) Piezoresponse force microscopy (PFM) amplitude and phase images showing clear ferroelectric switching characteristics. (d) PUND-measured hysteresis loop confirming the intrinsic ferroelectricity of the SATO film. The SATO film exhibits a high remanent polarization of 7.8 μC/cm² and excellent fatigue resistance. Scale bars: two μm. (Image by IMR)