Ultrahigh Thermal Conductivity of Cubic Boron Arsenide with an Unexpectedly Strong Temperature Dependence

Materials with high thermal conductivity are needed to conduct heat away fromhot spots in power electronics and optoelectronic devices. Cubic boron arsenide(c-BAs) has a high thermal conductivity due to its special phonon dispersionrelation. Previous experimental studies of c-BAs report a room-temperaturethermal conductivity between 1000 and 1300 watts per meter-kelvin. Wesynthesized high purity c-BAs single crystals with room-temperature thermalconductivity of 1500 watts per meter-kelvin. We observed its thermalconductivity to be proportional to the inverse square of temperature between300 and 600 kelvin, a stronger dependence than predicted by state-of-the-arttheory.