β-phase gallium oxide (Ga2O3) is an emerging ultrawide bandgap (UWBG) semiconductor (E G ∼ 4.8 eV), which promises generational improvements in the performance and manufacturing cost over today’s ...commercial wide bandgap power electronics based on GaN and SiC. However, overheating has been identified as a major bottleneck to the performance and commercialization of Ga2O3 device technologies. In this work, a novel Ga2O3/4H-SiC composite wafer with high heat transfer performance and an epi-ready surface finish has been developed using a fusion-bonding method. By taking advantage of low-temperature metalorganic vapor phase epitaxy, a Ga2O3 epitaxial layer was successfully grown on the composite wafer while maintaining the structural integrity of the composite wafer without causing interface damage. An atomically smooth homoepitaxial film with a room-temperature Hall mobility of ∼94 cm2/Vs and a volume charge of ∼3 × 1017 cm–3 was achieved at a growth temperature of 600 °C. Phonon transport across the Ga2O3/4H-SiC interface has been studied using frequency-domain thermoreflectance and a differential steady-state thermoreflectance approach. Scanning transmission electron microscopy analysis suggests that phonon transport across the Ga2O3/4H-SiC interface is dominated by the thickness of the SiN x bonding layer and an unintentionally formed SiO x interlayer. Extrinsic effects that impact the thermal conductivity of the 6.5 μm thick Ga2O3 layer were studied via time-domain thermoreflectance. Thermal simulation was performed to estimate the improvement of the thermal performance of a hypothetical single-finger Ga2O3 metal–semiconductor field-effect transistor fabricated on the composite substrate. This novel power transistor topology resulted in a ∼4.3× reduction in the junction-to-package device thermal resistance. Furthermore, an even more pronounced cooling effect is demonstrated when the composite wafer is implemented into the device design of practical multifinger devices. These innovations in device-level thermal management give promise to the full exploitation of the promising benefits of the UWBG material, which will lead to significant improvements in the power density and efficiency of power electronics over current state-of-the-art commercial devices.
We report on vertical β-Ga2O3 power diodes with oxidized-metal Schottky contact (PtOx) and high permittivity (high-κ) dielectric (ZrO2) field plate to improve reverse blocking at both Schottky ...contact surfaces and edges. The PtOx diodes showed excellent forward transport with near unity ideality factor and similar minimum specific on-resistance as Pt. Moreover, the PtOx contacts facilitated higher breakdown voltage and lower leakage current due to their higher Schottky barrier height (SBH) by more than 0.5 eV compared to that of Pt. Most importantly, the reduced off-state leakage of PtOx diodes enabled orders of magnitude less power dissipation than Pt ones for all duty cycles ≤0.5, indicating their great potential to realize low-loss and efficient, high-power β-Ga2O3 switches. The ZrO2 field-oxide further reduced edge leakage with a consistent increase in breakdown voltage. Device simulation demonstrated that the high permittivity of ZrO2 also led to the peak electric field occurring in β-Ga2O3 instead of the dielectric. These results indicate that the combined integration of oxidized-metal contacts to increase SBH and high-κ dielectric field plate to assist edge termination can be promising to enhance the performance of vertical β-Ga2O3 Schottky diodes.
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