Gallium-nitride (GaN) power semiconductors are well-established, but compared with silicon (Si) devices, GaN is still an evolving power device technology. Most power designers have at least explored the use of GaN, whether it’s been depletion-mode (d-GaN) normally-on devices, enhancement-mode (e-GaN) normally-off devices, a cascode combination of a Si MOSFET with a d-GaN device to form a normally-off structure, or a GaN power IC. Those options continue to advance. More recently, high-voltage vertical GaN (v-GaN) devices have entered the commercial arena. This FAQ looks briefly at GaN HEMT physics, reviews the performance and tradeoffs between lateral d-GaN, and e-GaN, looks at integrated GaN solutions that can simplify power converter designs, and closes by presenting the emerging v-GaN technology.