【Member Papers】Deciphering the mechanism of enhanced scintillation properties in In-doped β-Ga₂O₃ ultrafast scintillation crystal

      Researchers from the Tongji University have published a dissertation titled "Deciphering the mechanism of enhanced scintillation properties in In-doped β-Ga₂O₃ ultrafast scintillation crystal" in Optics Express.

Background

      β-Ga₂O₃, an ultra-wide bandgap semiconductor (4.7–4.9 eV), offers a high critical electric field (∼8 MV/cm) and excellent stability, making it promising for high-power electronics making it promising for high-power electronics, deep ultraviolet detection, and solar-blind detection applications. Beyond electronic and optoelectronic devices, β-Ga₂O₃ is also a luminescent material. Luminescence refers to non-thermal light emission arising from radiative electronic transitions following excitation by an external energy source. When the excitation is provided by high-energy ionizing radiation, this light-emission process is referred to as scintillation, which represents a specific form of luminescence and is directly relevant to radiation detection applications. Recently, β-Ga₂O₃ has also emerged as a fast-decay scintillator with unique advantages for medical imaging, space detection, and particle identification. These include an ultrafast decay time (<10 ns), high theoretical light yield (∼40800 ph/MeV), strong radiation resistance, and feasibility of large-scale single-crystal growth by melt techniques. Although β-Ga₂O₃ shows great potential as a scintillator, its application in radiation detection is limited by slow decay components (hundreds of ns) and sub-theoretical light yield. Doping can tune its electronic structure and recombination dynamics, offering a route to improved performance. However, most dopants show trade-offs: Si⁴⁺ shortens decay but reduces light yield, whereas Al³⁺ and Cu²⁺ increase light output but slow the decay. These contrasting effects highlight the need for advanced doping strategies to achieve balanced scintillation properties in β-Ga₂O₃ crystals.

Abstract

      β-Ga₂O₃ is a promising ultrafast semiconductor scintillator, but its efficiency is hindered by low light yield and slow decay components. Here, high-quality β-Ga₂O₃:In single crystals were grown by the optical floating-zone method. In³⁺ incorporation narrows the bandgap (4.76 eV to 4.72 eV), redshifts photoluminescence, strengthens electron–phonon coupling, and accelerates recombination, with a 91 meV activation energy for blue-to-ultraviolet energy transfer. Compared to unintentionally doped (UID) β-Ga₂O₃, the β-Ga₂O₃:In bulk single crystal demonstrates enhanced light yields of (3348 ± 310) ph/MeV and (5664 ± 710) ph/5.5 MeV under 662 keV γ-ray and 5.5 MeV α-ray excitation, respectively, using Bi₄Ge₃O₁₂ (BGO) as the reference scintillator, together with a markedly faster nanosecond-scale decay. The improved performance is attributed to enhanced charge transport and carrier recombination, highlighting its potential for ultrafast radiation detection.

Conclusion

      In summary, high-quality β-Ga₂O₃:In bulk single crystals were successfully synthesized, and their luminescence and scintillation properties systematically investigated. About 1 at% In³⁺ doping reduces the bandgap by 0.04 eV. UVL and BL exhibit distinct electron–phonon coupling with effective phonon energies of 38 and 44 meV, respectively, and enhanced UVL-to-BL energy transfer (E_a2 = 91 meV) leads to anomalous thermal BL enhancement. In³⁺ doping also leads to enhanced scintillation performance. Under 662 keV γ-ray excitation, using a commercial BGO scintillator as the reference, the light yield increases from (2797 ± 270) to (3348 ± 310) ph/MeV, while the fast component (∼4 ns) is preserved and the slow component is shortened from 331.3 ns (84.3%) to 148.5 ns (73.0%). Under 5.5 MeV α-ray excitation, β-Ga₂O₃:In exhibits a higher light yield (5664 ± 710 ph/5.5 MeV) compared with the UID β-Ga₂O₃ (5428 ± 650 ph/5.5 MeV), together with an increased fast-component fraction and a reduced contribution from the slow component. A comprehensive model incorporating band structure changes and carrier pathways explains the enhanced light yield and accelerated decay. This study provides fundamental insights into β-Ga₂O₃:In luminescence and highlights its potential for ultrafast scintillators and advanced optoelectronic applications.