Research Projects

"The thermal conductivity of semiconducting crystals, such as boron phosphide (BP), silicon carbide (SiC), and boron arsenide (BAs), typically increases monotonically when hydrostatically compressed. However, a recent study predicts that this conventional picture fails for three cubic compound semiconductors: boron phosphide (BP), silicon carbide (SiC), and boron arsenide (BAs). The study predicts a non-monotonic pressure-dependence of their thermal conductivities around and beyond room temperature, driven by an unusual pressure-driven interplay among phonon-phonon scattering channels. This interplay leads to a giant enhancement (~two-fold) of the thermal conductivity of these materials at low pressures (~30 GPa) followed by a precipitous drop at higher pressures, which has never been experimentally observed in any material. The proposal aims to experimentally demonstrate the initial rapid rise and subsequent precipitous drop in the thermal conductivity of these three cubic compound semiconductors for the first time, confirming a realistic pathway to rapidly enhance their ultrahigh thermal conductivities for applications in cooling specialized high-power electronics. The researchers will hydrostatically compress these materials to extreme pressures (~70 GPa) in a diamond-anvil cell and measure their pressure-dependent thermal conductivities using a non-contact optical pump-probe experiment called the transient grating. This enhancement of the phonon bottleneck effect on carrier thermalization under hydrostatic pressure could pave the way for highly efficient and ultrasensitive photo-detectors with extended photo-excited carrier lifetimes."