Photoluminescence properties of in situ Tm-doped AlxGa1−xN

Abstract

We report on the photoluminescence ͑PL͒ properties of in situ Tm-doped Al x Ga 1Ϫx N films (0рx р1) grown by solid-source molecular-beam epitaxy. It was found that the blue PL properties of Al x Ga 1Ϫx N:Tm greatly change as a function of Al content. Under above-gap pumping, GaN:Tm exhibited a weak blue emission at ϳ478 nm from the 1 G 4 → 3 H 6 transition of Tm 3ϩ . Upon increasing Al content, an enhancement of the blue PL at 478 nm was observed. In addition, an intense blue PL line appeared at ϳ465 nm, which is assigned to the 1 D 2 → 3 F 4 transition of Tm 3ϩ . The overall blue PL intensity reached a maximum for xϭ0.62, with the 465 nm line dominating the visible PL spectrum. Under below-gap pumping, AlN:Tm also exhibited intense blue PL at 465 and 478 nm, as well as several other PL lines ranging from the ultraviolet to near-infrared. The Tm 3ϩ PL from AlN:Tm was most likely excited through defect-related complexes in the AlN host.

Thermal quenching of luminescence and isovalent trap model for rare‐earth‐ion‐doped AlN

“…ions lines in AlN [4,11,13,18,19] and GaN hosts [8,10,20,21]. In contrast to the CL spectra, the PL spectra show broadband background overlapping with RE ion emissions.…”

“…Spectra are artificially shifted up for better visualization. Such luminescence intensity changes can be explained by temperature-dependent crossrelaxation ( 3 F 3 transitions, respectively, however, the possibility of other transitions is not completely ruled out [4,11]. In contrast to the PL spectrum, the CL of Tm-doped AlN is dominated by the group of blue lines centered at ~466 nm originating from …”

Spectroscopic studies of the infrared emission from Tm doped Al x Ga 1– x N thin films

“…2 b). [6,7]. Several researchers have studied the IR emission from Tm doped materials using Judd-Ofelt analysis and reported branching ratios of less than ~1% for the F 2 transitions [8,9].…”

Cathodoluminescence and its temperature dependence in Tm‐doped Al x Ga 1– x N thin films

“…Moreover, we have investigated several methods for enhancement of blue emission from GaN:Tm ELDs in both brightness and efficiency, including the "photopumping" method [4] and optimization [5] of the growth temperature. We have recently reported enhanced blue EL [6] emission and photoluminescence [7] (PL) emission from in-situ Tm-doped Al x Ga 1-x N films. This was made possible by using the bandgap engineering method based on the fact that III-V alloys of GaN-AlN span a large bandgap energy, ranging from 3.4 to 6.2 eV.…”