Study on single-crystal growth and X-ray detection performance of Ni-doped β-Ga2O3

Semiconductor X-ray detectors have attracted considerable attention recently owing to their high sensitivity and excellent stability. Among them, semi-insulating β-Ga 2 O 3 stands out due to its superior thermal stability, high breakdown electric field, and high crystal quality, enabling the fabrication of high-performance detectors suitable for various working environments. In this study, Ni 2+ was introduced into β-Ga 2 O 3 as a deep-level acceptor via doping engineering. A high-resistivity Ni-doped β-Ga 2 O 3 crystal was grown using the edge-defined film-fed growth (EFG) method. X-ray fluorescence spectrometer (XRF) confirmed a Ni doping concentration of 0.544 at%. The crystal exhibited a rocking curve with a full width at half maximum (FWHM) of 65.13 arcsec and clear, symmetric Laue patterns. The ultraviolet–visible (UV–Vis) transmission spectrum showed a cutoff edge at 265.5 nm, yielding a bandgap of 4.67 eV. Moreover, the semi-insulating behavior of Ni: β-Ga 2 O 3 was indicated by the infrared absorption edge extended beyond 10 μm. Raman spectroscopy revealed lattice distortion due to Ni 2+ incorporation, causing shifts in peak positions and intensities without phase change. A metal–semiconductor–metal (MSM)-structured X-ray detector based on Ni: β-Ga 2 O 3 was fabricated and characterized under various biases and dose rates. The device exhibited excellent stability at 1000 V with a high sensitivity of 663.36 μC/Gy·cm 2 , outperforming detectors from other semi-insulating β-Ga 2 O 3 crystals due to its superior crystal quality and high breakdown strength. Furthermore, low oxygen vacancy concentration contributed to fast response times of 0.20 s (rise) and 0.23 s (fall). The detection limit was estimated to be 12.04 nGy/s, highlighting its potential for low-dose X-ray detection.