Vapor‐Flux Growth of c‐BP Single Crystals With Concurrently High Electrical Resistivity and Isotope‐Enhanced High Thermal Conductivity

Cubic boron phosphide (c-BP) is another class of high thermal conductivity material alongside cubic boron arsenide (c-BAs) and diamond, as a promising candidate semiconductor for thermal management applications. Here, we report a new vapor-flux growth method that enables the growth of several mm-size crystals with significantly reduced defect densities, impurity inclusions, and achieving room temperature resistivity as high as 600 Ω cm. The resistivity value is much higher than previous reports and approaches the semi-insulating regime, a desirable characteristic of semiconductors. Most notably, the isotope-enriched c-¹⁰BP shows thermal conductivity values that are significantly higher than natural c-BP and c-¹¹BP across a wide temperature range. Specifically, at room temperature the corresponding values are ≈600 W m^-1 K^-1, 488 W m^-1 K^-1 and 540 W m^-1 K^-1, respectively. This enhancement is attributed to the weaker anharmonic phonon-phonon interaction in c-¹⁰BP compared to c-¹¹BP, as explained by first principles calculations.