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The increasing complexity of semiconductor devices fabricated from wide-bandgap and ultra-wide-bandgap materials demand advanced thermal management solutions to mitigate heat buildup, a major cause of device failure. High thermal conductivity materials are thus becoming crucial for thermal management. Cubic boron arsenide (c-BAs) has emerged as a promising candidate. However, challenges remain in synthesizing high-quality crystals with low defect concentrations, high homogeneous thermal conductivity, and high yields using the conventional chemical vapor transport method. In this study, we report the synthesis of high-yield c-BAs single crystals using the Bridgman method. The crystals exhibit high uniformity, reduced defect densities, and lower carrier concentrations as confirmed through x-ray diffraction, Raman spectroscopy, temperature-dependent photoluminescence, and electrical transport measurements. Our work represents a significant step toward scalable production of high-quality c-BAs for industrial applications, offering a practical solution for improving thermal management in next-generation electronic devices. 

β-Ga2O3 has attracted much recent attention as a promising ultrawide bandgap semiconductor. Hydrogen can affect the conductivity of β-Ga2O3 through the introduction of shallow donors and the passivation of deep acceptors. The introduction of H or D into β-Ga2O3 by annealing in an H2 or D2 ambient at elevated temperature produces different classes of O–H or O–D centers. This work is a study of the interaction of D with VGa1 and VGa2 deep acceptors as well as other impurities and native defects in Ga2O3 by infrared spectroscopy and the complementary theory. (We focus primarily on the deuterium isotope of hydrogen because the vibrational modes of O–D centers can be detected with a higher signal-to-noise ratio than those of O–H.) O–D centers in β-Ga2O3 evolve upon annealing in an inert ambient and are transformed from one type of O–D center into another. These reactions affect the compensation of unintentional shallow donors by deep acceptors that are passivated by D. Defects involving additional impurities in β-Ga2O3 compete with VGa deep acceptors for D and modify the deuterium-related reactions that occur. The defect reactions that occur when D is introduced by annealing in a D2 ambient appear to be simpler than those observed for other introduction methods and provide a foundation for understanding the D-related reactions that can occur in more complicated situations. 

While a number of O-H and O-D vibrational lines have been observed for hydrogen and deuterium in β-Ga2O3, it has been commonly reported that there is no absorption with a component of the polarization E parallel to the [010], or b, axis. This experimental result has led to O-H defect structures that involve shifted configurations of a vacancy at the tetrahedrally coordinated Ga(1) site [VGa(1)] and have ruled out structures that involve a vacancy at the octahedrally coordinated Ga(2) site [VGa(2)], because these structures are predicted to show absorption for E//[010]. In this Letter, weak O-D lines at 2475 and 2493 cm−1 with a component of their polarization with E//[010] are reported for β-Ga2O3 that had been annealed in a D2 ambient. O-D defect structures involving an unshifted VGa(2) are proposed for these centers. An estimate is made that the concentration of VGa(2) in a Czochralski-grown sample is 2–3 orders of magnitude lower than that of VGa(1) from the intensities of the IR absorption lines. 

Substitutional impurities in Ga2O3 are used to make the material n-type or semi-insulating. Several O-D vibrational lines for OD-impurity complexes that involve impurities that are shallow donors and deep acceptors have been reported recently. The present paper compares and contrasts the vibrational properties of complexes that involve shallow donors (OD-Si and OD-Ge) with complexes that involve deep acceptors (OD-Fe and OD-Mg). Complementary theory investigates the microscopic structures of defects that can explain the observed vibrational properties.