Alleviating trade-off between dark current and sensitivity of β-Ga2O3 X ray detector 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 reduces μτ product, thereby limiting detection sensitivity. In this paper, we report a defect engineering strategy by introducing gallium vacancy (VGa) and decreasing concentration of oxygen vacancy (Vo) via air annealing, which achieves simultaneous enhancement of both resistivity (1.48×1010 Ω cm) and 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 0.193 nA and a high sensitivity of 1394 μC Gyair-1 cm-2 under a low bias voltage of 40 V, which is nearly 70 times higher than 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 the 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.