【Domestic Paperes】"Complementary Material Integration": Co‑Optimizing Low Noise and High Signal in X‑Ray Detectors for High Detectivity via β-Ga₂O₃/3D/2D Metal Halide Perovskite Heterojunction

      Researchers from the“State Key Laboratory of Crystal Materials, Institute of Novel Semiconductors, Institute of Crystal Materials, Shandong University, and Shenzhen Research Institute of Shandong University” have published a dissertation titled "Complementary Material Integration: Co-Optimizing Low Noise and High Signal in X-Ray Detectors for High Detectivity via β-Ga₂O₃/3D/2D Metal Halide Perovskite Heterojunction" in Advanced Functional Materials.

Background

      X‑rays have been widely used in medical imaging, security inspection, and industrial flaw detection. Given the hazards of ionizing radiation, adherence to the as low as reasonably achievable (ALARA) principle is imperative. To achieve high‑contrast imaging under low‑dose conditions, detectors must exhibit both high sensitivity and low detection limits. In x‑ray detectors, sensitivity mainly depends on the electron‑hole pair creation energy, carrier mobility‑lifetime (µτ) product, x‑ray absorption efficiency, and photoconductive gain of the semiconductor material. The detection limit, on the other hand, is determined by the signal‑to‑noise ratio (SNR). High‑resistivity materials are essential to ensure low dark current, thereby minimizing noise. However, single semiconductor materials can hardly combine high resistivity, low electron‑hole pair creation energy and high µτ product. Silicon shows poor X‑ray absorption; amorphous selenium (a‑Se) possesses low µτ product. Although cadmium zinc telluride (CZT) delivers good performance, its commercialization is hindered by challenges in scalable crystal growth, compositional uniformity, and defect density control. As a fourth‑generation semiconductor, β-Ga₂O₃ features high density, tunable resistivity and good radiation hardness. Nevertheless, high‑resistivity doping degrades µτ product and reduces sensitivity. Metal halide perovskites (MHPs) have strong X‑ray absorption and large µτ product. Three‑dimensional (3D) MHPs provide high sensitivity yet suffer low resistivity and severe ion migration. Two‑dimensional (2D) MHPs obtain high resistivity at the cost of deteriorated carrier transport. Intrinsic performance trade‑offs exist in single‑material systems, calling for innovative strategies to break such bottlenecks.

Abstract

      Achieving high-contrast imaging under low-dose x-rays is a core challenge for x-ray detectors, as co-optimizing low dark current and high sensitivity in a single material remains difficult. Herein, we propose a complementary material integration (CMI) strategy by combining a high resistivity wide bandgap oxide with a high µτ product perovskite. This strategy is demonstrated in the x-ray detector based on a β-Ga₂O₃/3D/2D metal halide perovskite (MHP) heterostructure. The high resistivity of β-Ga₂O₃ ensures low noise, while its combination with a 2D MHP layer effectively passivates the 3D MHP active layer, yielding both high performance and enhanced stability. The detector exhibits a large µτ product of 1.61 × 10⁻³ cm² V⁻¹, a dark current of only 1.09 pA at 100 V, and a high sensitivity of 7140 µC Gy_air ⁻¹ cm⁻². These properties yield a high quasi-detectivity (S√A/I_Dark) of 354.86 C Gy⁻¹ cm⁻¹ A⁻¹/² and a low detection limit of 8.16 nGy s⁻¹. Furthermore, the detector realizes high-contrast imaging (SNR = 138.0) for x-rays at the medically safe dose (2.944 µGy s⁻¹). This study successfully realizes the co-optimization of low dark current, high sensitivity, and low detection limit, and provides a CMI strategy for high-performance x-ray imaging devices.

Highlights

      The research team puts forward the complementary material integration (CMI) strategy. Instead of using one single semiconductor to fulfill all performance requirements, this strategy distributes functions between high‑resistivity oxide for low‑noise and perovskite with high mobility‑lifetime (µτ) product for high signal, overcoming the intrinsic trade‑off between resistivity and carrier transport.

      β-Ga₂O₃/3D MAPbBr₃/2D MA₃Bi₂I₆Br₃ heterojunction devices are constructed. β-Ga₂O₃ acts as high-resistivity X-ray absorber. The 2D perovskite passivates defects and suppresses ion migration of 3D perovskite, and restrains dark current via band offset. The 3D perovskite guarantees efficient carrier transport.

      At 100 V bias, the device delivers ultralow dark current of 1.09 pA, high sensitivity of 7140 µC Gy_air⁻¹ cm⁻², ultra-low detection limit of 8.16 nGy s⁻¹, and superior quasi-detectivity compared with most reported oxide- and perovskite-based X-ray detectors. Dark-current drift is also greatly mitigated.

      High-quality imaging with SNR = 138.0 is achieved at medically safe dose rate (2.944 µGy s⁻¹). The heterojunction detector also exhibits self-powered detection capability and decent ambient storage stability, showing promising prospects for clinical low-dose X-ray imaging.

Conclusion

      In this work, we propose a CMI strategy that combines a high resistivity wide bandgap oxide with a high µτ product perovskite. We demonstrate this strategy by fabricating an x‑ray detector based on a β-Ga₂O₃/3D/2D MHP heterojunction, which exhibits an outstanding µτ product of 1.61 ×10⁻³ cm² V⁻¹ and a low dark current drift of 3.57 ×10⁻⁷ nA cm⁻¹ s⁻¹ V⁻¹. The detector demonstrates a high sensitivity of 7140 µC Gy_air⁻¹ cm⁻² at 100 V bias, combined with a low dark current of only 1.09 pA and a detection limit as low as 8.16 nGy s⁻¹. Benefiting from this combination of low dark current and high sensitivity, the detector achieves a high quasi‑detectivity of 354.86 C Gy⁻¹ cm⁻¹ A⁻¹ᐟ², enabling high‑contrast imaging (SNR=138) under low‑dose x‑rays at 2.944 µGy s⁻¹. This study successfully realizes the synergistic optimization of low dark current, high sensitivity, and a low detection limit through the CMI strategy, providing a viable solution for the development of high‑performance x‑ray imaging devices with a low detection limit.

Project Support

      This work was financially supported by the National Key Research and Development Program of China (2024YFA1208800), the Shenzhen Fundamental Research Program (Grant No. GJHZ20220913142605011), National Natural Science Foundation of China (NSFC) (Grant Nos. 52572176, U23A20358), Natural Science Foundation of Shandong Province (Grant Nos. ZR2023ZD05 and 2022TSGC2120), and National Key Laboratory of Solid-State Microwave Devices and Circuits (No. 2025LB015-4).