Enhancing the luminescence yield of Cr³⁺ in β-Ga₂O₃ by proton irradiation

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.