Combinatorial synthesis and characterization of thin film Al1-xRExN (RE = Pr3+, Tb3+) heterostructural alloys

• Main Authors: Paudel, Binod, Mangum, John S, Rom, Christopher L, Egbo, Kingsley, Lee, Cheng-Wei, Guthrey, Harvey, Allen, Sean, Haegel, Nancy M, Yazawa, Keisuke, Brennecka, Geoff L, Smaha, Rebecca W
• Format: Journal Article
• Language: English
• Published: 14-08-2024
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.2408.07848

The potential impact of cation-substituted AlN-based materials, such as
Al1-xScxN, Al1-xGaxN, and Al1-xBxN, with exceptional electronic,
electromechanical, and dielectric properties has spurred research into this
broad family of materials. Rare earth (RE) cations are particularly appealing
as they could additionally impart optoelectronic or magnetic functionality.
However, success in incorporating a significant level of RE cations into AlN
has been limited so far because it is thermodynamically challenging to
stabilize such heterostructural alloys. Using combinatorial co-sputtering, we
synthesized Al1-xRExN (RE = Pr, Tb) thin films and performed a rapid survey of
the composition-structure-property relationships as a function of RE alloying.
Under our growth conditions, we observe that Al1-xPrxN maintains a phase-pure
wurtzite structure until transitioning to amorphous for x>0.22. Al1-xTbxN
exhibits a phase-pure wurtzite structure until x<0.15, then exhibits mixed
wurtzite and rocksalt phases for 0.16<x<0.28, and finally becomes amorphous
beyond that. Ellipsometry measurements reveal that the absorption onset
decreases with increasing rare earth incorporation and has a strong dependence
on the phases present. We observe the characteristic cathodoluminescence
emission of Pr3+ and Tb3+, respectively. Using this synthesis approach, we have
demonstrated incorporation of Pr and Tb into the AlN wurtzite structure up to
higher compositions levels than previously reported and made the first
measurements of corresponding structural and optoelectronic properties.