Three semiconductors, three jobs
If you're designing circuits in 2026, you're probably using one of three semiconductors: silicon (Si), gallium arsenide (GaAs), or gallium nitride (GaN). Each wins a different category, and the question is almost never which is \"best\" — it's which is right for your voltage, frequency, and cost budget.
The three numbers that actually matter
- Band gap — how much energy it takes to move an electron from valence to conduction band. Si: 1.1 eV, GaAs: 1.4 eV, GaN: 3.4 eV. Wider band gap = handle more voltage before breakdown.
- Electron mobility — how fast electrons actually move. GaAs: 8,500 cm²/V·s, Si: 1,400, GaN: 2,000 (but 2D gas is ~2,200 in HEMT structures).
- Thermal conductivity — how well heat leaves the chip. Si: 150 W/m·K, GaN: 130, GaAs: 55. (SiC, for comparison: 490 — the highest of common semiconductors, which is why it dominates high-power inverters.)
Silicon (Si): the default for a reason
Silicon's position isn't about performance — GaAs and GaN beat it on many metrics. It's about manufacturing. Silicon wafers are mature to 300 mm diameter, yield is 99%+, and the entire world's semiconductor fab capacity optimizes for it. A silicon logic chip costs pennies per transistor. GaN and GaAs are orders of magnitude more expensive.
Use silicon for: logic (CPUs, memory, FPGAs), power electronics under 100 V, audio and lower-frequency RF, MEMS, image sensors (CMOS).
GaAs: where speed pays
GaAs has electron mobility 6× silicon's. That translates to much faster switching — up to 100 GHz in modern HBT transistors. Where that actually matters:
- Cellular basestation power amplifiers (up to ~40 GHz for 5G mmWave).
- Satellite transceivers.
- Radar frontends.
- High-efficiency photovoltaic cells (up to 30% single-junction, vs ~22% for silicon — but 10× the price).
- Infrared and red LEDs (AlGaAs).
Downsides: brittle (GaAs wafers are fragile), expensive (4× silicon), thermally poor (heat dissipates slowly). You don't use it unless RF performance demands it.
GaN: the power-electronics disruptor
Wide band gap means GaN devices can hold off much higher voltages in smaller die areas, and switch faster without breaking. The math:
- A 650 V GaN switch is ~1/5 the size of a 650 V silicon MOSFET.
- Switching losses are 3–10× lower.
- Switching frequency can be 1–10 MHz (vs ~200 kHz for silicon).
That's why a GaN phone charger fits 100 W in a pocket. And why data-center power supplies, EV onboard chargers, and solar inverters are all moving GaN. The premium is real — GaN devices cost 2–4× silicon — but the system savings (smaller heatsinks, smaller inductors, less PCB area) more than pay it back above 100 W.
The 2026 semiconductor picking chart
- CPU, GPU, RAM: Silicon. Forever.
- Power management (under 100 V): Silicon.
- Laptop / phone charger (100–300 W): GaN.
- EV onboard charger (600–800 V): GaN or SiC.
- EV drive inverter (800 V+): SiC.
- Solar inverter: SiC or GaN.
- 5G base station RF (28 GHz): GaAs or GaN.
- Satellite transceiver: GaAs.
- Radar (3–100 GHz): GaAs or GaN.
- Red / infrared LED: AlGaAs or AlGaInP.
- Blue / white LED: GaN (InGaN).
- Efficient photovoltaic (space satellite): GaAs multi-junction.
- Ground-mount solar farm: Silicon — price wins.
Look them up side by side
MaterialsLab has Si, GaAs, and GaN with crystal system, density, and band gap. Use compare mode to see all three at once. Free, no card.