What are SiC-MOSFETs? – Comparison of Power Transistor Structures and Features

In succession to the preceding section, we compare different power transistors. This time, we compare their structures and features.

Comparison of Power Transistor Structures and Features

The following graphic compares the structures, rated voltages, ON-resistances, and switching speeds of various power transistors.

Structures differ depending on the process technology used, and the electrical characteristics are also different. Incidentally, DMOS is a general element structure that is a planar-type MOSFET. With Si power MOSFETs, both a high voltage and a reduced ON-resistance can be obtained, and in recent years super-junction structure MOSFETs (hereafter SJ-MOSFETs) have come into widespread use. We have presented a DMOS structure as an example of a SiC-MOSFET, but at present, ROHM is mass-producing trench-structure SiC-MOSFETs with further improved characteristics. We will be describing these devices in more detail in the future.

Features of the different element types are as described in the radar charts above. ON-resistance is an issue with Si-DMOS’s, and as explained above, by adopting a SJ-MOSFET structure, the ON-resistance is improved. IGBTs have superior ON-resistances and rated voltages, but switching speed is a problem. SiC-DMOS’s are switching elements which excel with respect to rated voltage, ON-resistance, and switching speed alike, and have the further major advantage of satisfactory operation at high temperatures.

This graph plots the normalized ON-resistances and rated voltages of various transistors. As is clear from the graph, theoretically SiC-DMOS enables the fabrication of transistors with high voltages and low ON-resistances. Current SiC-DMOS elements have characteristics within the region of the ellipse; further developments are expected to result in improved performance.

Next time, we will describe separate comparisons with SiC-MOSFET devices.

• MOSFET
• SiC-DMOS