Ion-beam-induced luminescence (IBIL) measurements were performed in Cr-doped β-Ga₂O₃ using both protons and helium ions, showing a strong enhancement of the Cr³⁺ luminescence upon ion irradiation. Theoretical modelling of the IBIL intensity curves as a function of the fluence allowed estimating the effective cross-sections associated with the defect-induced IBIL enhancement and quenching processes. The results suggest that sensitizing the Cr³⁺ luminescence is more efficient for H⁺ than for He⁺ irradiation. Thermoluminescence (TL) studies were performed in the pristine sample, with no TL signal being observed in the spectral region corresponding to the Cr³⁺ emission. In agreement with the IBIL study, upon ion irradiation (with either protons or helium ions), this TL emission is activated. Moreover, it can be quenched by annealing at 923 K for 10 s, thus revealing the role played by the defects induced by the irradiation. These results show that the irradiation-induced defects play a major role in the activation of the Cr³⁺ luminescence, a fact that can be exploited for radiation sensing and dosimetry.

In situ ion-beam-induced luminescence measurements reveal a strong enhancement of the Cr³⁺ emission yield in electrically conductive chromium doped β-Ga₂O₃ single crystals upon proton irradiation. The observed effect can be explained based on the Fermi-level pinning caused by radiation defects. This pinning of the Fermi level activates deep carrier traps that can act as sensitizers of the Cr³⁺ emission. In agreement with this model, in semi-insulating samples, where the Fermi level lies deep in the bandgap, the Cr³⁺ emission is present already in as-grown samples, and no enhancement of its intensity is observed upon proton irradiation. The boost of the Cr³⁺ emission yield by irradiation, observed in conductive samples, is reversed by thermal annealing in argon at temperatures above 550 °C for 30 s. The results reveal a high potential of Cr-doped β-Ga₂O₃ for in situ and ex situ optical radiation detection and dosimetry.

This paper reports a comprehensive study of single-phase polycrystalline chromium-doped zinc gallogermanate (ZGGO:Cr) synthesised by a high-temperature solid-state reaction, employing photoluminescence (PL), persistent luminescence (PersL) and thermoluminescence (TL) measurements. A bandgap energy of ∼4.77 eV (260 nm) was estimated by optical reflectance. The ZGGO:Cr luminescence was dominated by a red/near-infrared emission due to Cr³⁺ optical centres, which displayed well-resolved R1, R2, N1 and N2 lines, and a broad vibronic progression. PL excitation (PLE) data revealed that those centres were preferentially populated via intraionic absorption, being also excited via band-to-band absorption and by a defect excitation band at ∼0.9 eV below the conduction band, whose origin remains unknown. PersL of more than 10 h was identified and attributed to the N2 Cr³⁺-related defect. The TL results suggest a continuous distribution of electronic states with activation energies ranging from about 0.7 eV to 1.2 eV. An effective density of states was obtained for different delay times between irradiation and heating, revealing a rapid depopulation for activation energies below ∼1 eV. In short, this research contributes to a better understanding of traps in ZGGO:Cr and highlights the potential of the Cr³⁺-related emission in this material for dosimetric purposes, paving the way for developing novel ZGGO:Cr-based devices.

β-Ga2O3 is a promising material for power electronics due to its wide bandgap and high breakdown field, but its low thermal conductivity poses challenges for heat dissipation. To address this, we employed ion beam exfoliation to fabricate β-Ga2O3 nanomembranes integrated with highly thermally conductive Si substrates. To do this, chromium ion implantation was used to induce stress and strain, forming rolled-up microtubes on (100)-oriented β-Ga2O3 single crystals. After successfully transferring these tubes onto Si substrates and performing thermal annealing, these microtubes were unrolled into nanomembranes. X-ray diffraction and Raman measurements revealed the high quality of the samples. Time-domain thermoreflectance was used to study thermal transport in these structures, confirming uniform thermal conductivity across three fabricated samples. A Debye-based thermal transport model was implemented to validate experimental results and define the main phonon scattering mechanisms. Non-equilibrium molecular dynamics simulations revealed that a thin amorphous SiO2 interlayer significantly enhanced the thermal boundary conductance (TBC) across the β-Ga2O3/Si interface by bridging the vibrational mismatch between β-Ga2O3 and Si. However, further increasing the interlayer thickness led to phonon scattering and reduced TBC, emphasizing the importance of precise interface thickness control. This study highlights ion beam exfoliation as a scalable approach for integrating β-Ga2O3 with thermally conductive substrates, providing a pathway to improved thermal management in β-Ga2O3-based power electronics.

Chromium-doped Ga2O3, with intense Cr3+-related red-infrared light emission, is a promising semiconductor material for optical sensors. This work constitutes a comprehensive study of the thermoluminescence properties of Cr-, Mg-codoped beta-Ga2O3 single crystals, both prior to and after proton irradiation. The thermoluminescence investigation includes a thorough analysis of measurements with different beta(-) irradiation doses used to populate the trap levels, with preheating steps to disentangle overlapping peaks (T-M-T-STOP and initial rise methods) and finally by computationally fitting to a theoretical expression. At least three traps with activation energies of 0.84, 1.0, and 1.1 eV were detected. By comparison with literature reports, they can be assigned to different defect complexes involving oxygen vacancies and/or common contaminants/dopants. Interestingly, the thermoluminescence signal is enhanced by the proton irradiation while the type of traps is maintained. Finally, the pristine glow curve was recovered on the irradiated samples after an annealing step at 923 K for 10 s. These results contribute to a better understanding of the defect levels in Cr-, Mg-codoped beta-Ga2O3 and show that electrons released from these traps lead to Cr3+-related light emission that can be exploited in dosimetry applications.