High Thermal Conductivity in Isotopically Enriched Cubic Boron Phosphide.

Zinc blende boron arsenide (BAs), boron phosphide (BP), and boron nitride (BN) have attracted significant interest in recent years due to their high thermal conductivity (Λ) predicted by first‐principles calculations. This research reports the study of the temperature dependence of Λ (120 K < T < 600 K) for natural isotope‐abundance BP and isotopically enriched 11BP crystals grown from modified flux reactions. Time‐domain thermoreflectance is used to measure Λ of sub‐millimeter‐sized crystals. At room temperature, Λ for BP and 11BP is 490 and 540 W m−1 K−1, respectively, surpassing the values of conventional high Λ materials such as Ag, Cu, BeO, and SiC. The Λ of BP is smaller than only cubic BN, diamond, graphite, and BAs among single‐phase materials. The measured Λ for BP and 11BP is in good agreement with the first‐principles calculations above 250 K. The quality of the crystals is verified by Raman spectroscopy, X‐ray diffraction, and scanning transmission electron microscopy. By combining the first‐principles calculations and Raman measurements, a previously misinterpreted Raman mode is reassigned. Thus, BP is a promising material not only for heat spreader applications in high‐power microelectronic devices but also as an electronic material for use in harsh environments. Thermal conductivities of high quality natural‐abundance BP and isotopically‐enriched 11BP single crystals measured between 120–600 K using time‐domain thermoreflectance show good agreement with theoretical calculation, surpassing many conventional high‐thermal‐conductivity materials at above 300 K. Such high intrinsic thermal conductivities, combined with their outstanding chemical inertness and high mechanical hardness, suggest their potential applications for heat dissipation in high‐power electronics. [ABSTRACT FROM AUTHOR]