Infineon CoolMOS

What it is

CoolMOS is a family of high-voltage power transistors (MOSFETs) from Infineon Technologies, headquartered in Neubiberg near Munich. It was released in 1998 and is regarded as the first commercial product based on the superjunction concept. Infineon has since developed numerous generations of the technology for different voltage classes and applications.

How it works

Power MOSFETs switch electrical current on and off in power supplies and converters. In conventional designs there is a trade-off: to block high voltages, the drift region of the transistor must be thick and lightly doped, which increases its resistance when switched on and causes losses. A superjunction transistor overcomes this by using alternating n-type and p-type pillars in the drift region. These compensate each other's charge when blocking voltage, so the region can be more heavily doped and the on-resistance falls significantly for the same voltage rating.

Why it stands out

Lower resistance means less energy is lost as heat, so power supplies can be smaller, cooler and more efficient. That matters at a time when power electronics are central to data centres, electric vehicles, renewable energy and consumer electronics. Superjunction technology has become a standard approach in high-voltage silicon MOSFETs, and other manufacturers have developed their own versions. CoolMOS helped establish Infineon as one of the world's leading suppliers of power semiconductors.

Where you meet it

CoolMOS transistors sit inside chargers for laptops and phones, server and telecom power supplies, LED lighting drivers, solar inverters and charging stations for electric cars. They are invisible to users, but they make the devices smaller and more energy-efficient.