Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

Under realistic switching conditions, SiC MOSFETs reliability issues remain as a challenge that requires further investigation. In this letter, a specific aging test has been developed to monitor and characterize the electrical parameters of the SiC MOSFET. This allows estimations of the health state and predictions of the remaining lifetime prior to its failure. The gate leakage current seems to be a relevant runaway parameter just before failure. This leakage indicates deterioration of the gate structure. This hypothesis has been validated through analysis of scanning electron microscopy pictures, with a focused ion beam cut showing cracks within the polysilicon.

This paper reports on the fabrication technology and packaging strategy for 300-V 5-A silicon carbide Schottky diodes with a wide temperature operation range capability (between -170 °C and 300 °C). These diodes have been designed for harsh environment space applications such as inner Solar System exploration probes. Different endurance tests have been performed to evaluate the diode behavior when working at a high temperature and under severe thermal cycling conditions (ranged from -170 °C to 270 °C). The radiation hardness capability has been also tested. It has been found that the hermeticity of the package in a neutral atmosphere is a key aspect to avoid an electrical parameter drift. Moreover, the use of gold metallization and gold wire bonds on the anode allows reducing the diode surface and bonding degradation when compared to Al-containing technology. On the back-side cathode contact, the Ti/Ni/Au metallization and AuGe combination have shown a very good behavior. As a result, the manufactured diodes demonstrated high stability for a continuous operation at 285 °C.

Currently, the demand by new application scenarios of increasing operating device temperatures in power systems is requiring new die-attach materials with higher melting points and suitable thermomechanical properties. This makes the die-attach material selection, die-attaching process, and thermomechanical evaluation a real challenge in nowadays power packaging technology. This paper presents a comparative analysis of the thermomechanical performance of high-temperature die-attach materials (sintered nano-Ag, AuGe, and PbSnAg) under harsh thermal cycling tests. This study is carried out using a test vehicle formed by four dice (considering Si and SiC semiconductors) and Cu substrates. Thermally cycled test vehicles have been thermomechanically evaluated using die-shear tests and acoustic microscopy inspections. Besides, special attention is paid to set up a nano-Ag sintering process, in which the effects of sintering pressure or substrate surface state (roughness and surface activation) on the die-attach layer are analyzed. As a main result, this study shows that the best die-attach adherence is obtained for nano-Ag when pressure is applied on the dice (using a specifically designed press) during the sintering process (11 MPa provided die-shear forces of 53 kgf). However, this die-attach presents a faster thermomechanical degradation under harsh thermal cycling tests than other considered high-temperature die-attach materials (AuGe and PbSnAg) and PbSnAg shows the best thermomechanical performances.

We have studied the electrocaloric response of the archetypal antiferroelectric $\mathrm{PbZr}{\mathrm{O}}_3$ as a function of voltage and temperature in the vicinity of its antiferroelectric-paraelectric phase transition. Large electrocaloric effects of opposite signs, ranging from an electrocooling of −3.5 K to an electroheating of $+5.5\mathrm{K}$, were directly measured with an infrared camera. We show by calorimetric and electromechanical measurements that the large negative electrocaloric effect comes from an endothermic antiferroelectric-ferroelectric switching, in contrast to dipole destabilization of the antiparallel lattice, previously proposed as an explanation for the negative electrocaloric effect of antiferroelectrics.