Who makes GaN and SiC inside for AI data centers

The power shelf takes rack-level AC or DC in and hands regulated DC to the busbar. Wide- bandgap devices sit inside its conversion stages, and the reason they are there is the same as on the board — lower switching loss and higher frequency — but the constraint is different. A shelf occupies rack units, and every rack unit it takes is a rack unit not holding compute, so the pressure is on power density as much as on efficiency. This is the higher-voltage half of the wide-bandgap story, which is why silicon carbide features more here than on the board. The front-end AC-DC stage and the isolation stage behind it run at voltages where SiC's advantage is clearest, and efficiency at those stages is compounded: every watt lost in conversion is a watt drawn from the utility, paid for in the power contract, and removed again by the cooling plant. AI racks made this acute by raising rack power sharply, and the industry's move toward higher-voltage DC distribution inside the rack pushes further in the same direction. What to look for is where a device maker sits in the chain — some sell devices to the power- shelf builders, some sell modules, and the shelf builders themselves appear in the parent part — and whether wafer or substrate supply is in-house, since that has gated wide- bandgap output before.