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Ultra-wide band gap semiconductor devices based on β-phase gallium oxide (Ga2O3) offer the potential to achieve higher switching performance and efficiency and lower manufacturing cost than that of today’s wide band gap power electronics. However, the most critical challenge to the commercialization of Ga2O3 electronics is overheating, which impacts the device performance and reliability. We fabricated a Ga2O3/4H–SiC composite wafer using a fusion-bonding method. A low-temperature (≤600 °C) epitaxy and device processing scheme was developed to fabricate MOSFETs on the composite wafer. The low-temperature-grown epitaxial Ga2O3 devices deliver high thermal performance (56% reduction in channel temperature) and a power figure of merit of (∼300 MW/cm2), which is the highest among heterogeneously integrated Ga2O3 devices reported to date. Simulations calibrated based on thermal characterization results of the Ga2O3-on-SiC MOSFET reveal that a Ga2O3/diamond composite wafer with a reduced Ga2O3 thickness (∼1 μm) and a thinner bonding interlayer (<10 nm) can reduce the device thermal impedance to a level lower than that of today’s GaN-on-SiC power switches. 

Abstract β -Ga 2 O 3 metal–semiconductor field-effect transistors are realized with superior reverse breakdown voltages ( V BR ) and ON currents ( I DMAX ). A sandwiched SiN x dielectric field plate design is utilized that prevents etching-related damage in the active region and a deep mesa-etching was used to reduce reverse leakage. The device with L GD = 34.5 μ m exhibits an I DMAX of 56 mA mm −1 , a high I ON / I OFF ratio >10 8 and a very low reverse leakage until catastrophic breakdown at ∼4.4 kV. A power figure of merit (PFOM) of 132 MW cm −2 was calculated for a V BR of ∼4.4 kV. The reported results are the first >4 kV class Ga 2 O 3 transistors to surpass the theoretical unipolar FOM of silicon. 

This paper discusses the terahertz electromagnetic response of metallic gratings on anisotropic dielectric substrates. The metallic gratings consist of parallel gold stripes. Utilizing numerical simulations, we observe that it is possible to excite a series of resonant modes in these structures. These modes are affected differently by the different indices on the anisotropic substrate. An analytical model is discussed to show that modes associated with transmission peaks are due to the excitation of (a) Fabry–Pérot modes with polarization along the grating and/or (b) waveguide modes with polarization perpendicular to the grating. It is observed that the resonance associated with the TM_1,1mode is a narrow linewidth resonance which, in some particular circumstances, becomes nearly independent of substrate thickness. Therefore, from the spectral position of this resonance, it is possible to extract the out-of-plane component of the substrate refractive index with very small uncertainty. Based on this observation, we demonstrate the refractive index characterization of several lossless semiconductor substrates through frequency-domain polarized terahertz transmission measurements in the frequency range of 0.2–0.6 THz at normal incidence. The reliability of the technique is demonstrated on well-known materials, such as high-resistivity silicon and sapphire substrates. This technique is also applied for the characterization of a Fe-doped β-Ga₂O₃single-crystal substrate.

 

High quality dielectric‐semiconductor interfaces are critical for reliable high‐performance transistors. This paper reports the in situ metal–organic chemical vapor deposition of Al₂O₃on β‐Ga₂O₃as a potentially better alternative to the most commonly used atomic layer deposition (ALD). The growth of Al₂O₃is performed in the same reactor as Ga₂O₃using trimethylaluminum and O₂as precursors without breaking the vacuum at a growth temperature of 600 °C. The fast and slow near interface traps at the Al₂O₃/β‐Ga₂O₃interface are identified and quantified using stressed capacitance–voltage (CV) measurements on metal oxide semiconductor capacitor (MOSCAP) structures. The density of shallow and deep level initially filled traps (D_it) are measured using ultraviolet‐assisted CV technique. The average D_itfor the MOSCAP is determined to be 6.4×10¹¹cm⁻²eV⁻¹. The conduction band offset of the Al₂O₃/ Ga₂O₃interface is also determined from CV measurements and found out to be 1.7 eV which is in close agreement with the existing literature reports of ALD Al₂O₃/Ga₂O₃interface. The current–voltage characteristics are also analyzed and the average breakdown field is extracted to be approximately 5.8 MV cm⁻¹. This in situ Al₂O₃dielectric on β‐Ga₂O₃with improved dielectric properties can enable Ga₂O₃‐based high‐performance devices.