The aims of this study are (i) to demonstrate the synthesis of Cr3+-activated β-Ga2O3 films by metal-organic deposition and (ii) to report the temperature-dependent photoluminescence (PL) properties of such films from 20 to 300 K. An activation energy of ∼0.9 eV for the Cr3+ ions in β-Ga2O3 is determined from a plot of PL intensity vs calcination temperature. The red-line emission doublet R1 and R2 at ∼1.8 eV and the broad emission band with a peak at ∼1.7 eV are ascribed to the Cr3+ ions in the β-Ga2O3 host. The energies of the excited states, i.e., 2E, 4T2, 2T2, 4T1, and 4T1, in Cr3+ are determined from the experimental PL and PL excitation spectra using a newly developed analysis model. The high-energy luminescence tail of the broad 4T2 → 4A2 emission band can be explained by the hot-carrier effect of the photoexcited electrons in the 4T2 state. The relative intensities of the R-line emission doublet can also be explained very well by the population and depopulation of the electron numbers in the E¯ (R1) and 2A¯ (R2) states. PL properties, such as the temperature-dependent PL intensity, peak energy, and spectral width, are analyzed in detail.

We demonstrate the synthesis of β-Ga2O3:Eu3+ red-emitting films by metal–organic deposition and report the photoluminescence (PL) properties of such films measured from 20 to 450 K. β-Ga2O3 is one of five well-known modifications of gallium oxide. The X-ray diffraction analysis indicates that only β-phase Ga2O3 can be synthesized by calcination at T c≥800 °C. An activation energy of ∼0.65 eV for the Eu3+ ions in β-Ga2O3 is determined from a plot of Eu3+-related red emission intensity vs calcination temperature. Lattice temperature dependences of the PL spectrum and luminescence decay time were performed at T = 20–450 and 20–300 K, respectively. No strong temperature dependences of the red emission intensity and decay time were observed below 300 K; however, the PL intensity at T > 300 K exhibited a gradual decrease with increasing T, yielding a quenching energy of ∼0.5 eV. The films calcined at T c≥900 °C revealed a deep-red emission band peaking at ∼1.7 eV, together with two sharp red emission peaks at ∼1.78 and ∼1.80 eV. These emission band and peaks were attributed to the Cr3+ ions unintentionally doped in β-Ga2O3.

We synthesize Ga2O3:Tb3+ green phosphor by metal-organic deposition and report the photoluminescence (PL) properties of this phosphor. The X-ray diffraction analysis indicates that only β-phase Ga2O3:Tb3+ can be synthesized by calcination at Tc = 700°C. The Tb3+-related green emission intensity shows an increase with increasing molar ratio M = Tb/Ga and a saturation at M ∼ 0.005 − 0.03, followed by the concentration quenching at M > 0.03. The decreased luminescence decay time caused by the concentration quenching is clearly observed at M > 0.03. The green emission intensity exhibits a gradual decrease with increasing temperature above ∼300 K, yielding quenching energies of 0.25 and 0.63 eV. The detailed energy-level scheme of Tb3+ ions in β-Ga2O3 is obtained from the PL and PL excitation spectra of this phosphor.