This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phaseshifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and the system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case.Index Terms-AC-DC power converters, battery charger, dc-dc power converters, electric vehicles (EVs), power electronics, silicon carbide (SiC).

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Characteristics of hafnium silicate as gate dielectric in n-GaN capacitors were investigated. The Hf0.57Si0.43Ox, Hf0.64Si0.36Ox and HfO2 films exhibited high dielectric constants of 15.4, 15.9, and 17.6, respectively. The Hf0.57Si0.43Ox and Hf0.64Si0.36Ox films, which had an amorphous structure, showed superior properties, including a minimal flatband voltage (Vfb) hysteresis (≤70 mV) and a small Vfb shift (≤−0.45 V), as well as a low interface state density (~4 × 1011 cm−2 eV−1 at −0.4 eV from conduction band), and a high breakdown electric field (≥8.6 MV cm−1) compared to those of a polycrystalline HfO2 film.

This paper presents the feasibility of highly reliable and repeatable copper–tin transient liquid phase (Cu–Sn TLP) bonding as applied to die attachment in high temperature operational power modules. Electrified vehicles are attracting particular interest as eco-friendly vehicles, but their power modules are challenged because of increasing power densities which lead to high temperatures. Such high temperature operation addresses the importance of advanced bonding technology that is highly reliable (for high temperature operation) and repeatable (for fabrication of advanced structures). Cu–Sn TLP bonding is employed herein because of its high remelting temperature and desirable thermal and electrical conductivities. The bonding starts with a stack of Cu–Sn–Cu metal layers that eventually transforms to Cu–Sn alloys. As the alloys have melting temperatures (Cu3Sn: > 600 °C, Cu6Sn5: > 400 °C) significantly higher than the process temperature, the process can be repeated without damaging previously bonded layers. A Cu–Sn TLP bonding process was developed using thin Sn metal sheets inserted between copper layers on silicon die and direct bonded copper substrates, emulating the process used to construct automotive power modules. Bond quality is characterized using (1) proof-of-concept fabrication, (2) material identification using scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis, and (3) optical analysis using optical microscopy and scanning acoustic microscope. The feasibility of multiple-sided Cu–Sn TLP bonding is demonstrated by the absence of bondline damage in multiple test samples fabricated with double- or four-sided bonding using the TLP bonding process.

We systematically investigated characteristics of Pt-gated capacitors with four kinds of gate insulators such as Hf0.57Si0.43Ox, Hf0.64Si0.36Ox, HfO2, and Al2O3. The Hf0.64Si0.36Ox films fabricated by post-deposition annealing (PDA) at 800°C in O2 (PDO), N2(PDN), and 3% H2 (PDH) ambient exhibited quite different characteristics. After PDO, the Hf0.64Si0.36Ox film was partially crystallized and had a thick interfacial layer at the n-GaN/Hf0.64Si0.36Ox interface, while the Hf0.64Si0.36Ox films after PDN and PDH maintained an amorphous structure. The PDH capacitor exhibited an order of magnitude larger interface state density than the PDN capacitor, indicating that the PDN process can produce superior Hf0.64Si0.36Ox film. The Hf0.57Si0.43Ox,Hf0.64Si0.36Ox, HfO2, and Al2O3 films after PDA at 800°C in N2 were 15.4, 15.9, 17.6, and 9, respectively. The HfO2 and Al2O3 films consist of polycrystalline structure while the Hf0.57Si0.43Ox and Hf0.64Si0.36Ox films maintain an amorphous structure. The different structure strongly affected to electrical properties. The Hf0.57Si0.43Ox and Hf0.64Si0.36Ox capacitors showed superior electrical properties such as a minimal flatband voltage (V fb) hysteresis ( ≤ +70 mV) and a small V fb shift ( ≤ -0.46 V), as well asa low interface state density (~ 3 × 1011 cm-2eV-1 at -0.45 eV fromconduction band), and a high breakdown electric field ( ≥ 8.6 MV/cm) compared to those of the HfO2 and Al2O3 capacitors.