Alleviating trade-off between dark current and sensitivity of β-Ga2O3 X ray detectors via defect engineering

Abstract

In recent years, Ga₂O₃ has attracted great attention in the field of X-ray detectors. However, β-Ga₂O₃ exhibits low resistivity due to intrinsic shallow donor impurities, leading to detectors with a high dark current. Acceptor ion doping can increase resistivity, while simultaneously reducing the μτ product, thereby limiting detection sensitivity. In this paper, we report a defect engineering strategy by introducing gallium vacancies (V_Ga) and decreasing the concentration of oxygen vacancies (V_o) via air annealing, which achieves simultaneous enhancement of both resistivity (1.48 × 10¹⁰ Ω cm) and the µτ product (5.04 × 10⁻⁴ cm² V⁻¹). Experiments demonstrate that the β-Ga₂O₃ annealed single crystal (SC) detector exhibits a low dark current of 0.139 nA and a high sensitivity of 1394 µC Gy_air⁻¹ cm⁻² under a low bias voltage of 40 V, which is nearly 70 times higher than that of commercial amorphous Se detectors. In addition, the β-Ga₂O₃ annealed SC detector has an ultralow detection limit of 35.1 nGy s⁻¹, far lower than 5500 nGy s⁻¹ required for conventional medical diagnosis. Furthermore, this study demonstrates the imaging capability of the β-Ga₂O₃ SC X-ray detector. By addressing the intrinsic conflict between dark current and sensitivity in β-Ga₂O₃, this work provides a novel design strategy for developing high performance X-ray detectors.