A transistor is a tiny electronic switch that opens and closes very quickly, and GaN has several advantages over silicon when used in transistors. Not only are GaN transistors smaller than silicon transistors, they can carry more power, switch faster (about 40 million times per second, roughly four times faster than silicon transistors), and are much more energy efficient.
While silicon transistors have a power efficiency of around 87%, GaN transistors increase this efficiency to over 95%.
Reducing transistor size means that newer GaN USB chargers can be physically smaller than older silicon-powered chargers. And while it’s nice to have smaller chargers, the most important factor when it comes to USB chargers is increased efficiency, as the more efficient an electronic component is, the less waste heat it generates.
It’s understandable that consumers are concerned when chargers get warm to the touch. While it’s common for chargers using silicon transistors to get to the point of being almost too hot to touch, I find it odd that a charger using GaN technology would get even slightly warm.
Faster switching also means that a GaN transistor inside a charger can have better control over charging and respond to events like overheating or overvoltage much faster than older transistors, making them safer to use.