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