Ga₂O₃-on-SiC Composite Wafer for Thermal Management of Ultrawide Bandgap Electronics

Abstract

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.

Ultra-Wide Band Gap Ga2O3-on-SiC MOSFETs

“…24 Details of the SSTR setup used in this study are described in our previous work. 15 The pump and probe lasers were focused on the samples using the following microscope objectives: (i) a 2.5× objective (NA = 0.08) with pump and probe laser radii of 19.4 and 12.4 μm, respectively, and (ii) a 10× objective (NA = 0.25) with pump and probe laser radii of 5 and 4.3 μm, respectively. The thermal conductivity of the Ga 2 O 3 layer of the composite substrate was measured using a 10× objective to confine the probing volume within the Ga 2 O 3 layer.…”

“…Details of this combined approach using SSTR, TDTR, and FDTR methods as well as analytical modeling to estimate the effective TBR at the Ga 2 O 3 /SiC interface (including the measurement sensitivity analyses) can be found in our previous work. 15 The TBR of the composite wafer is lower than the value (60 m 2 K/GW) that was shown to be necessary to reduce the junction-to-package thermal resistance of a Ga 2 O 3 -on-SiC device below that of a commercial GaN-on-Si power switch. 13 However, it is 3× higher than the value reported for a Ga 2 O 3 / SiC interface joined with a 30 nm Al 2 O 3 bonding layer.…”

“…This switching frequency limit can be further increased by the implementation of top-side cooling solutions such as a diamond passivation overlayer 61 and flip-chipping. 62 A recent computational study 15 has predicted that practical multi-finger devices would experience significantly aggravated self-heating (a 4× higher channel temperature than singlefinger Ga 2 O 3 devices under identical power density conditions) due to the thermal cross-talk 16 among adjacent current channels. This trend has been experimentally confirmed by an experimental study 17 on multichannel Ga 2 O 3 FinFETs.…”

Bonding‐Enhanced Interfacial Thermal Transport: Mechanisms, Materials, and Applications

“…And the ITCs of Ga 2 O 3 /SiC range from 20 to 100 MW m −2 K −1 . [87][88][89] Zheng et al [90] prepared polystyrene thin films/sapphire samples and evaluated the relationship of interface bonding strength and rotation speed in the spin-coating process. With increasing spin-coating speed, the interfacial bonding strength increases gradually, and the ITC increases.…”

Insights into the Interfacial Contact and Charge Transport of Gas-Sensing Liquid Metal Marbles

“…Altogether, Ga 2 O 3 plays the role of an inert layer that protects the Ga-based liquid metals from further oxidation. Additionally, this layer is n-type Ga 2 O 3 that has a very wide band gap of 4.8 eV . Subsequently, when WO 3 /EGaIn contact is studied, the influence of the two oxides (WO 3 and Ga 2 O 3 ) of different electronic and morphological properties on the interfacial charge transport behavior of the liquid metal marble needs to be explored.…”