Luminescence of Eu ions inAlxGa1−xNacross the entire alloy composition range

Abstract

Photoluminescence ͑PL͒ and PL excitation ͑PLE͒ spectra of Eu-implanted Al x Ga 1−x N are obtained across the whole alloy composition range. The dominant 5 D 0 -7 F 2 emission band broadens and then narrows as x increases from 0 to 1 while the peak shifts monotonically. This behavior is surprisingly similar to the broadening of excitons in a semiconductor alloy caused by composition fluctuations ͓E. F. Schubert et al., Phys. Rev. B 30, 813 ͑1984͔͒. PLE spectra reveal a steplike Al x Ga 1−x N band-edge absorption and two "subgap" bands X 1,2 :X 1 peaks at 3.26 eV in GaN and shifts linearly to 3.54 eV in AlN. For x Ͼ 0.6, X 2 emerges approximately 1 eV higher in energy than X 1 and shifts in a similar way. We propose that X 1,2 involve creation of coreexcitonic complexes of Eu emitting centers.

Eu3+ luminescence properties of Eu- and Mg-codoped AlGaN

“…While the full widths of half maximum (FWHMs) of peaks A and B were 2.3 and 3.0 meV, the FWHMs of peaks B 1 and B 2 were increased to 3.8 and 4.1 meV, respectively. The increase in the FWHMs with increasing N Al could result from alloy disorder [15].…”

“…It is well known that an increase in the bandgap of the host material contributes to suppressing the thermal quenching of PL intensity [1]. In fact, when the optical properties of Eu-, Tb-, Er-, and Tm-implanted AlGaN were evaluated, an increase in the Al composition resulted in an increase in the PL intensity from RE ions at RT owing to the suppression of the back-transfer process [2,[15][16][17]. Therefore, the use of AlGaN with larger bandgap is promising to improve the luminescence efficiency.…”

Functionalizing self-assembled GaN quantum dot superlattices by Eu-implantation

“…Nevertheless, it is well known that broad absorption bands below the band gap of AlN and AlGaN alloys allow the excitation of Eu 3+ at this wavelength. 29 All the implanted and annealed SL and epilayer samples evidence Eu 3+ emission in the red spectral region. The PL intensity of the SL samples increases with the implantation fluence.…”

“…PLE on the Eu 3+ -lines in AlN:Eu shows a second broad absorption band peaked at ϳ345 nm. In AlN:Eu, these two bands were labeled as X 2 and X 1 , respectively, by Wang et al 29 and interpreted as excitonic features associated with a specific Eu 3+ center. The observation of these two absorption bands in Euimplanted AlN samples was also reported by other authors.…”

“…The most intense luminescence of Eu 3+ in these nitride hosts is known to arise from the 5 D 0 → 7 F 2 transition which occurs at ϳ624 nm in the AlN host and is blueshifted in GaN by ϳ2.2 nm. 29,30 Furthermore, Eu 3+ ions are known to give rise to multiple active centers in the binary systems. 31,32 In this context, it is important to emphasize the difference of the lattice site location of Eu ͑Eu is known to be incorporated into near-substitutional Ga and Al sites in GaN and AlN, respectively 25,26 ͒ and the different optically active centers ͑often also called "sites"͒ which depend on the local symmetry around the substitutional Eu ͑which can for example be influenced by next neighbor defects͒.…”