- you need a high breakdown voltage, so that for a given voltage you want to switch you can make the transistor channel as short as possible; shorten the physical distance that charge carriers have to flow in the semiconductor.
- you need a high maximum drift velocity, which governs the rate at which charge carriers can flow through the semiconductor
Those contribute to reducing the on-resistance of the transistor, thereby decreasing its heat output for a given size.
There are two factors:
- you need a high breakdown voltage, so that for a given voltage you want to switch you can make the transistor channel as short as possible; shorten the physical distance that charge carriers have to flow in the semiconductor.
- you need a high maximum drift velocity, which governs the rate at which charge carriers can flow through the semiconductor
Those contribute to reducing the on-resistance of the transistor, thereby decreasing its heat output for a given size.