Papers by Keyword: On-State Resistance

Abstract: In addition to the well-known bias temperature instability (BTI) phenomena, recently, it has been revealed that SiC MOSFETs show another instability during high-frequency repetitive switching between VGS(L) and VGS(H), referred to as gate-switching instability (GSI). This study shows the increase in switching energy caused by gate-switching instability VGS(th) drift as key performance parameters in electric power conversion systems, especially, when operating in hard-switching mode. A new methodology based on double pulse test was applied at each readout. The results highlighted the significance of the degradation mechanism through its impact on hard-switching applications with high-switching frequency. Therefore ruggedness against GSI plays a pivotal role in the long-term reliable operation of SiC MOSFET devices to ensure durable and efficient power conversion systems.

Abstract: SiC power MOSFETs show very promising electrical performance for efficient and reliable high temperature operation. This work presents a novel approach for the determination of the temperature dependence of SiC power MOSFET’s channel and drift resistance components in the on-state, which are extracted based on current-voltage (I-V) and capacitance-voltage (C-V) measurements without the need of data extrapolation. The results show that the channel resistance has weak, whereas the drift resistance has strong temperature dependence.

Abstract: The photoconductive semiconductor switches (PCSS) were fabricated on V-doped semi-insulating 6H-SiC. We studied the effect of surface morphology on the on-state resistance of SiC PCSS. The SiC wafers with quite similar physical properties were processed by mechanical polishing, chemical mechanical polishing and H2 etching for producing different surface morphologies. All the SiC PCSS were excited by a 355 nm laser with a frequency of 10 Hz and a pulse intensity of 132 μJ/mm². We found that the surface morphology had an obvious effect on the on-state resistance. The PCSS fabricated on mechanical polished SiC wafer with an average surface roughness (rms) of 1.0 nm showed the largest on-state resistance of 45.6 ohms, while a low value of 13.3 ohms was observed for the wafer processed by H2 etching at high temperature of 1550 °C.

Abstract: Although recent fast I-V measurements and subthreshold analysis reveal that the threshold-voltage instability due to low-field bias stressing at room temperature is greater than previously reported when calculated using slower, standard measurements by a parameter analyzer—a result that is consistent with electrons directly tunneling into and out of near interfacial oxide traps, this effect will not prevent the use of power SiC DMOSFET switches in power converter applications if certain precautions are followed. Namely, if the threshold voltage is set high enough so that a negative shift in threshold voltage will not increase the leakage current in the off-state, then the primary effect will be to increase the on-state resistance by decreasing the effective gate voltage. The instability due to ON-state stressing is greater than that for bias stressing alone, but not significantly. For a well behaved device, a 1-hour ON-state stress will result in about a 7 percent increase in conduction losses, which is manageable for power converter applications.

Abstract: Specific on-resistance Ron estimated from current density-voltage characteristics of Schottky diodes on thick layers exhibits variations from tens of mW.cm2 to tens of W.cm2 for different doping levels. In order to understand the occurrence of high on-state resistance, Schottky barrier heights were first estimated for both forward and reverse bias with the application of thermionic emission theory and were in agreement with a literature reported values. Decrease in mobility with the temperature was observed and its dependencies of T–1.3 and T–2.0 for moderately doped and low doped samples respectively were estimated. From deep level measurements by Minority Carrier Transient Spectroscopy, an influence of shallow boron related levels and D-center on dependence of on-state resistance was observed, being more pronounced in low doped samples. Similar tendency was observed in depth profiling of Ron. This suggests a major role of boron in a compensation mechanism thus resulting in high Ron.