Novel Design for Highly Sensitive, Fast High-Energy Photon Detector

Prof. LONG Shibing and his teamfrom the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) proposed a novel strategy for high-energy photon detector with high sensitivity and response speed by coupling the interface pyroelectric effect with the photoconductive effect based on polycrystal Ga-rich GaOx (PGR-GaOx) Schottky photodiode. Their work was published in Advanced Materials.

High-energy photon detectors (from deep ultraviolet (DUV) to X-rays) are crucial for various fields including national security, medicine, industrial science and so on.However, current semiconductor materials such as Si and α-Se suffer from large leakage currents and low X-ray absorption coefficients, making it difficult to meet the demands of high-performance detection. In contrast, wide bandgap (WBG) semiconductor GaO has shown great potential in high-energy photon detection. But the unavoidable deep energy level traps and the lack of effective device structure design of GaO have made it challenging to achieve high-energy photon detectors with high sensitivity and high response speed based on WBG semiconductor.

To address these challenges, Prof. LONG Shibing's team designed a pyroelectric photoconductive diode (PPD) based on PGR-GaOx for the first time. By coupling the interface pyroelectric effect with the photoconductive effect, the detection performance was significantly enhanced. The PPD exhibits high sensitivity to both DUV and X-ray, with responsivities up to 10⁴ A W^-1 and 10⁵ μC Gy _air^-1 cm^-2, respectively, which are over 100 times higher than previous detectors made from similar materials. In addition, the interface pyroelectric effect induced by polar symmetry in the depletion region of PGR-GaOx can greatly improve the response speed of the detector by 10⁵times, reaching up to 0.1 ms.

Schematic of the PPD based on PGR-GaO_Xfilm and its photoresponse compared to traditional photodiode. (Image by Prof. LONG Shibing's team)

Compared to traditional photodiodes, the PPD in self-powered mode generates higher gain at the moment of light switching due to the pyroelectric field. Moreover, the PPD can operate in bias mode, where the gain is highly dependent on the bias voltage. Ultra-high gain can be achieved by increasing the bias voltage.

PPD has great potential for applications in imaging enhancement systems with low energy consumption and high sensitivity. This work not only demonstrates that GaOx is a highly promising high-energy photon detector material, but also provides new strategies for realizing high-performance high-energy photon detectors.

Paper Link: https://doi.org/10.1002/adma.202314249

(Written by LI Rui, edited by ZHANG Yihang, USTC News Center)