Mapping of Long-Wavelength Phonon Contribution in the Thermal Transport of Alloyed Semiconductor Superlattices.

Geng, Zhi-Ming; Zhang, Kedong; Wang, Meiyu; Zhou, Jian; Cheng, Yuanbo; Yan, Xue-Jun; Fan, Xing; Yuan, Ming-Qian et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

The mapping of long-wavelength phonons is important to understand and manipulate the thermal transport in multilayered structures, but it remains a long-standing challenge due to the collective behaviors of phonons. In this study, an experimental demonstration of mapping the long-wavelength phonons in an alloyed Al<sub>0.1</sub>Ga<sub>0.9</sub>As/Al<sub>0.9</sub>Ga<sub>0.1</sub>As superlattice system is reported. Multiple strategies to filter out the short- to mid-wavelength phonons are used. The phonon mean-free-path-dependent thermal transport properties directly demonstrate both the suppression effect of the ErAs nanoislands and the contribution of long-wavelength phonons. The contribution from phonons with mean free path longer than 1 μm is clearly demonstrated. A model based on the Boltzmann transport equation is proposed to calculate and describe the thermal transport properties, which depicts a clear physical picture of the transport mechanisms. This method can be extended to map different wavelength phonons and become a universal strategy to explore their thermal transport in various application scenarios.