Semiconductor Compound Wafers
Beyond silicon, a wide range of compound semiconductor wafers enable devices that require higher frequencies, greater power handling, or unique optical properties. Compound wafers are made from materials such as gallium arsenide (GaAs), gallium nitride (GaN), indium phosphide (InP), silicon carbide (SiC), and sapphire. These wafers are essential for RF, power electronics, LEDs, lasers, and emerging photonics applications. Unlike silicon wafers, compound wafers are more expensive, smaller in diameter, and often limited by material availability and crystal growth complexity.
Key Compound Wafer Types
- Gallium Arsenide (GaAs): High electron mobility; widely used in RF amplifiers, laser diodes, and LEDs.
- Gallium Nitride (GaN): Wide bandgap material; ideal for power electronics, 5G/6G RF, radar, and high-efficiency LEDs.
- Indium Phosphide (InP): High-frequency and optoelectronic devices, including fiber-optic communication lasers.
- Silicon Carbide (SiC): Wide bandgap substrate for power MOSFETs, diodes, and EV inverters.
- Sapphire (Al2O3): Insulating substrate used for GaN epitaxy, LEDs, and RF applications.
Compound Wafer Mapping
| Material | Growth Method | Wafer Size | Applications | Strategic Risk |
|---|---|---|---|---|
| GaAs | LEC, VGF | 100–150 mm | RF amplifiers, LEDs, lasers | Arsenic toxicity, supply chain limited |
| GaN | Epitaxy on sapphire, SiC, or Si; native GaN limited | 100 mm (native), 200 mm (on Si) | Power electronics, RF, radar, LEDs | Native wafer growth still constrained; high cost |
| InP | LEC, VGF | 75–100 mm | Optoelectronics, fiber-optic lasers | Indium supply tied to zinc smelting byproducts |
| SiC | PVT (sublimation) | 100–200 mm | Power MOSFETs, EV inverters, high-voltage diodes | Limited wafer size; high cost vs Si |
| Sapphire | Czochralski, Kyropoulos | 100–200 mm | GaN growth substrate, LEDs, RF | Large-scale supply; cost stable, but limited to niche use |
Key Considerations
- Wafer Size Limitations: Most compound wafers are smaller (100–200 mm) compared to silicon’s 300 mm standard, limiting economies of scale.
- Purity Challenges: Defect densities and impurities remain higher than in silicon wafers, impacting yields.
- Cost Premiums: Compound wafers can cost 10–50× more than silicon wafers of the same size.
- Strategic Dependence: Many rely on byproduct elements (Ga, In, Ge) or materials concentrated in China, raising supply chain risks.
FAQs
- Why not replace silicon with compound wafers? – Silicon offers unmatched scale, cost efficiency, and wafer sizes; compounds fill specific niches.
- Which compound wafer is most important today? – SiC for EV power electronics and GaN for RF/power are the fastest-growing markets.
- Are compound wafers more advanced? – Not necessarily; they target specialized use cases rather than mainstream CMOS logic.
- Who makes compound wafers? – Players include Wolfspeed (SiC), II-VI / Coherent (GaAs, InP), and Sumitomo Electric (GaN, GaAs).
