Band Gap Engineering in β‑Ga₂O₃ for a High-Performance X‑ray Detector

Gallium oxide (Ga₂O₃) attracts great attention in the field of X-ray detection because of its ultrawide band gap, high breakdown electric field, and high X-ray absorption coefficient. However, unintentionally doped Ga₂O₃ tends to have low resistivity because of the shallow donors provided by unintentionally doped impurity elements or intrinsic defects. Iron and magnesium ion doping can increase the resistivity of β-Ga₂O₃, but the carrier drift length and carrier collection efficiency are greatly reduced because of the introduction of deep-level impurities. Here, Al-doped β-Ga₂O₃ (β-Ga₂O₃:Al) single crystals with high resistivity are obtained through band gap engineering. The mechanism by which Al³⁺ doping can increase the resistivity of the β-Ga₂O₃ crystal is discussed. A β-Ga₂O₃:15%Al-based X-ray detector with high resistivity and quality is prepared. The detector demonstrates a high sensitivity of 851.6 μC Gy_air^–1 cm^–2, which is 42 times higher than that of the commercial amorphous Se X-ray detector. Furthermore, the detector exhibits a fast response speed and both rise time and decay time of less than 0.05 s. The high performance of the detector is attributed to the high resistivity and high quality of the crystal. This work presents a method to obtain high-performance X-ray detectors based on β-Ga₂O₃ single crystals through band gap engineering.