GaN is a binary III-V material. GaN has a bandgap of 3.4 eV. Silicon has a bandgap of 1.1 eV. Wide bandgap refers to higher voltage electronic band gaps in devices, which are larger than 1 electronvolt (eV).
A GaN high electron mobility transistor (HEMT) is a lateral device. The current flows from the source to the drain on the surface. Below the surface, AlGaN and GaN layers are grown on a silicon substrate.
GaN is used in RF and power electronics. In the power arena, GaN-on-silicon chips are used in 30- to 600-volt applications. GaN-on-silicon is fast, but it also suffers from a lattice mismatch, making it prone to defects in the fab. It also suffers from reliability issues and low thermal conductivity. And there are also questions whether GaN-on-silicon can scale.
Lateral GaN-on-silicon devices could hit the wall at 600 volts, prompting the need for a next-generation technology, namely bulk vertical GaN transistors. In vertical GaN devices, the electrons flow from the top to the bottom.
But bulk GaN substrates are limited to small sizes and are expensive, meaning GaN-on-GaN will play a limited role over the next decade, according to Lux Research. On the other hand, GaN-on-SiC could get some traction, possibly in the transportation market starting in 2017, according to Lux.