Investigation of the role of defects in the scintillation mechanism of Ga2O3 glass-ceramics

Ga2O3 is a wide bandgap semiconductor that has gained significant importance in recent years for the production of ionising radiation detectors [1]. It is used both as the active electrical component in microelectronic devices (such as Schottky barrier diodes) and directly as a radioluminescent material coupled with suitable photodetectors. In the latter application, pure undoped Ga2O3 single crystals have shown good light yield with an emission peak in the 380-420 nm range and a decay time of tens of nanoseconds [2]. This emission is due to donor-acceptor pair (DAP) recombination involving O and Ga vacancies and interstitial Ga. Most studies on the scintillation of Ga2O3 have focused on the monoclinic β phase, the most stable crystalline form. However, Ga2O3 exists in six known crystalline phases. Among these, the cubic defect spinel gamma phase can be obtained as nanocrystals embedded in glass matrices. While they share similar DAP recombination processes, γ-Ga2O3 generally exhibits superior photoluminescence performance compared to β-Ga2O3 [3], making this type of glass-ceramics a promising scintillating material [4]. Here, we present an evaluation of the role of defects in the scintillation mechanism of these glass-ceramics, as well as their potential in scintillating application. We investigated a sample with composition 7.5Li2O – 2.5Na2O – 20Ga2O3 – 35GeO2 – 35SiO2 mol%. Glasses were prepared using the melt-quenching method, followed by a two-step thermal treatment at 618°C for 3.5 hours and 640°C for 15 minutes, resulting in fully transparent glass-ceramics containing Ga2O3 crystals just a few nanometers in diameter. Trapping mechanisms were assessed by combining temperature-dependent X-ray and UV luminescence with thermally stimulated luminescence (Fig. 1). Experiments were also conducted on glasses with the same composition in their amorphous form before any thermally induced nanosegregation, glasses stripped of Ga to mimic the amorphous matrix, and free-standing γ-Ga2O3 nanoparticles. The results indicate an active role of defects closely associated with the presence of Ga, either within the nanoparticles or on their surfaces, with negligible contributions from defects located in the glass matrix.