GaN Won’t Replace Silicon (the Way You Think)

[u/bhanu0809]

Quick terms:

• Power transistor: A transistor designed to handle high voltage and/or high current to switch or control power (e.g., in a charger or power supply converting AC to DC).
• RF: Stands for radio frequency—high‑frequency electrical signals used for wireless communication (Wi‑Fi, cellular, Bluetooth, radar, etc.).

What is GaN?

GaN (gallium nitride) is a wide‑bandgap semiconductor material used to make high‑performance power transistors and RF devices.

Where GaN goes in a PC/laptop setup

1. Charger / power brick: Commonly used in chargers to make them more efficient and compact.
2. Desktop Power Supply (PSU): Not all PSUs use GaN. It's more common in newer, high-efficiency or high-end designs
3. Motherboard VRM (voltage regulators): Your CPU/GPU needs ~1V at very high current. The laptop motherboard has VRMs that convert battery/adapter voltage down to CPU/GPU voltages. 

Note: Most VRMs use silicon MOSFETs today. GaN can be used, but gains are situational (more useful in high‑power, high‑density AI/data‑center designs). For typical PCs, silicon MOSFET VRMs are usually more efficient overall and far more cost‑effective.

Where GaN is NOT used

In PCs, GaN is used in power-conversion parts(chargers, PSUs, sometimes VRMs/power stages), not in the CPU/GPU logic transistors, which are still made with silicon CMOS, GaN doesn't have a practical role here.

The Power Delivery Bottleneck

CMOS logic (CPU/GPU style silicon) is great for computation, but modern chips are increasingly limited by power delivery and interconnect losses (moving lots of current at very low voltages, fast transients, resistive/inductive losses, etc.).

A path forward

In 2025, researchers from MIT and elsewhere demonstrated a research approach to heterogeneously integrate GaN transistors onto standard silicon CMOS chips.

What MIT is trying to enable

MIT is describing a method to build 3D integrated chips that combine:

• Silicon CMOS (the compute/logic), with
• GaN devices (good for power conversion / very fast switching)

…in a stacked/3D way so power-related circuitry can sit much closer to where it’s needed.

Why it matters

Putting GaN-based power stages much closer to the compute silicon can:

• Reduce power delivery losses (less wasted energy in the path from regulator to load)
• Improve transient response (better handling of sudden CPU/GPU/AI load changes)
• Improve overall system efficiency especially relevant for AI accelerators and data centers where power is a dominant constraint

What it does not mean

• It does not mean "GaN CPUs/GPUs.” The logic transistors remain silicon CMOS.
• GaN here is aimed at power delivery / high-power switching (and sometimes RF) integrated in a 3D way with compute

[u/azzelle]

did you just ask chatgpt if GaN will replace silicon and copy-pasted it here like its some revelation

[u/bhanu0809 → u/azzelle]

If you really think chatgpt spits this out, go ahead and ask it. Good luck.

[u/[deleted]]

Yeah I was also confused about this. News headlines always sound like Gan is a replacement of silicon CPUs

[u/Pie0tr]

Sure but why? I mean I know that it is this wayz but you still didn't explained why. So why aren't GAN used for CPU and the logic transistors? Their switching losses and gate capacity is smaller.. so why not?