Packaged Ga₂O₃ Schottky Rectifiers With Over 60-A Surge Current Capability

Abstract

Ultra-wide-bandgap gallium oxide (Ga2O3) devices have recently emerged as promising candidates for power electronics; however, the low thermal conductivity (kT) of Ga2O3 causes serious concerns about their electrothermal ruggedness. This work presents the first experimental demonstrations of largearea Ga2O3 Schottky barrier diodes (SBDs) packaged in the bottom-side-cooling and double-side-cooling configurations, and for the first time, characterizes the surge current capabilities of these packaged Ga2O3 SBDs. Contrary to popular belief, Ga2O3 SBDs with proper packaging show high surge current capabilities. The double-side-cooled Ga2O3 SBDs with a 3×3 mm 2 Schottky contact area can sustain a peak surge current over 60 A, with a ratio between the peak surge current and the rated current superior to that of similarly-rated commercial SiC SBDs. The key enabling mechanisms for this high surge current are the small temperature dependence of on-resistance, which strongly reduces the thermal runaway, and the double-side-cooled packaging, in which the heat is extracted directly from the Schottky junction and does need to go through the low-kT bulk Ga2O3 chip. These results remove some crucial concerns regarding the electrothermal ruggedness of Ga2O3 power devices and manifest the significance of their die-level thermal management. 1

Low Thermal Resistance (0.5 K/W) Ga₂O₃ Schottky Rectifiers With Double-Side Packaging

“…The simulated R θJC and I-V characteristics were calibrated with the experimental data. The calibration revealed that the k T of the sintering region is ∼1 Wcm −1 K −1 [25], implying the room for further improvement of the sintering process. Table I benchmarks the R θJC of our Ga 2 O 3 SBDs against commercial 600-V SiC SBDs with a similar current rating and different TO-series packages (the wide-used packages for commercial power devices), as well as a small-area unpackaged Ga 2 O 3 SBD reported previously [14].…”

“…The device packaging process was similar to that in [25]. For die attach, a 50-μm-thick nanosilver paste was sintered without pressure at 250 • C [26].…”

“…Based on the measured R θJC , 3-D TCAD simulations were performed in Silvaco Atlas to evaluate the device R θ in various external cooling conditions. The electrothermal models were similar to [33], [34], and the material models (e.g., k T of Ga 2 O 3 and nano-Ag, interface R θ ) were based on [25]. A copper plate with a geometry similar to the experimental setup was added to the package surface where the external cooling is applied.…”

(Invited) How to Achieve Low Thermal Resistance and High Electrothermal Ruggedness in Ga2O3 Devices?

“…A nanosilver paste from NBE Technologies was then used for the die attach by a pressureless sintering process in air (31,32). More details on the sintering process were reported in (16). Devices with single-side-and double-side-cooled packages were then prototyped, as shown in Fig.…”

“…To fill these gaps, our team for the first time demonstrated large-area, packaged Ga2O3 devices and characterized their thermal resistance and transient electrothermal ruggedness. This paper reviews the key results, with the details published in (15)(16)(17)(18). Vertical Ga2O3 SBDs with a 3×3 mm 2 Schottky contact area were fabricated, showing a forward current over 20 A and a breakdown voltage (BV) over 600 V. Small-area Ga2O3 SBDs fabricated on the same wafer exhibited capabilities to operate at high temperatures up to 600 K (18).…”