SemiconductorX > Materials & IP > Wafer Production > Compound & Specialty Wafers
Compound & Specialty Wafers
Compound semiconductors are materials made from two or more elements -- silicon carbide (SiC), gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN) -- that enable device performance silicon cannot achieve. Higher electron mobility enables faster RF switching. Wider bandgap enables higher breakdown voltage and operating temperature. Direct bandgaps enable efficient light emission. These properties make compound wafers the substrate of choice for power electronics, RF amplifiers, photonics, defense, and optoelectronics. Each material class has its own crystal growth method, supplier landscape, and supply chain risk profile -- entirely separate from the silicon wafer supply chain.
Compound Wafer Landscape
| Material | Crystal Growth | Max Commercial Diameter | Primary Applications | Key Suppliers | Supply Chain Status |
|---|---|---|---|---|---|
| SiC (4H) | Physical Vapor Transport (PVT) at 2,100-2,400°C | 150mm in volume; 200mm in qualification | Power MOSFETs and Schottky diodes for EV inverters, solar, industrial drives; semi-insulating substrates for GaN RF epi | Wolfspeed (US), Coherent (US), SiCrystal/Rohm (DE), Onsemi/GTAT (US), SICC (CN), TanKeBlue (CN) | Transitioning; 150mm dominant, 200mm ramp underway; Chinese producers gaining share rapidly; see SiC Substrates page |
| GaAs | Liquid Encapsulated Czochralski (LEC) or Vertical Gradient Freeze (VGF) | 150mm (6-inch) mainstream; 200mm emerging for microLED | RF power amplifiers (5G phones), VCSEL arrays (3D sensing, datacom), solar cells, microLED displays | Sumitomo Electric (JP), AXT/Freiberger (US/DE, ~95% of substrate market combined); IQE (UK, epi) | Mature; highly consolidated substrate supply; epi outsourcing dominant for RF; see GaAs & InP page |
| InP | Vertical Gradient Freeze (VGF); Liquid Encapsulated Czochralski (LEC) | 100mm mainstream; 150mm emerging | Coherent optical transceivers (datacom/telecom), photonic integrated circuits, InP HEMTs for mmWave (100GHz+), space solar cells | Sumitomo Electric (JP), AXT (US), Freiberger (DE), JX Advanced Metals (JP) | Growing; AI-driven datacom demand accelerating; indium supply tied to zinc smelting; see GaAs & InP page |
| GaN (epiwafer) | MOCVD epitaxy on Si, SiC, or sapphire substrate; bulk GaN substrates exist but rare and costly | 200mm (GaN-on-Si, power); 150mm (GaN-on-SiC, RF); 200mm (GaN-on-sapphire, LED) | Power conversion (GaN-on-Si); RF amplifiers for defense and 5G (GaN-on-SiC); LEDs, laser diodes, and optoelectronics (GaN-on-sapphire) | EpiGaN/Soitec (BE/FR), IQE (UK), Wolfspeed (US, GaN-on-SiC), Enkris (CN), Innoscience (CN); LED IDMs (Nichia, San'an, Epistar) captive GaN-on-sapphire | Rapidly growing across all three platforms; substrate choice (Si vs SiC vs sapphire) is the defining supply chain decision; see GaN Epiwafers page |
| Sapphire (Al2O3) | Czochralski or Kyropoulos method from aluminum oxide melt at ~2,050°C | 200mm in LED production; larger boules exist for other applications | GaN-on-sapphire substrate for LED production (dominant historical use); RF isolation substrate; watch glass and optical windows (non-semiconductor) | Rubicon Technology (US), Kyocera (JP), Monocrystal (RU), Crystalwise (TW); multiple Chinese producers for LED-grade | Stable and well-supplied for LED volumes; thermally insulating (limits power/RF use); GaN-on-sapphire is being displaced by GaN-on-Si for power and GaN-on-SiC for RF; see GaN Epiwafers page for platform comparison |
Silicon vs Compound: Why the Materials Coexist
Compound semiconductors do not replace silicon -- they serve markets where silicon physics hits a ceiling. Silicon's bandgap (1.1 eV) limits its breakdown voltage and operating temperature. Its indirect bandgap makes it a poor light emitter. Its electron mobility, while adequate for digital logic, constrains RF performance at millimeter-wave frequencies. SiC (3.26 eV bandgap), GaN (3.4 eV), GaAs (1.42 eV direct bandgap), and InP (1.35 eV direct bandgap) each address one or more of these silicon limitations, but at higher substrate cost, smaller wafer sizes, and with entirely separate supply chains. The cost crossover point -- where a compound device's performance premium justifies the substrate premium -- defines each compound semiconductor's addressable market.
Supply Chain Outlook
The compound wafer supply chain is fragmented by material, with no single company spanning all four substrate types at scale. SiC is the highest-volume growth market, driven by EV power electronics, and is seeing the most aggressive Chinese producer entry. GaAs substrate supply is stable and highly consolidated among three Japanese/US/German producers. InP is growing rapidly on AI-driven datacom photonics demand. GaN epiwafer supply is bifurcated by application -- power GaN-on-Si and RF GaN-on-SiC have different substrate requirements, different supplier sets, and different supply chain risks.
Section Pages
SiC Substrates & Epiwafers | GaAs & InP Wafers | GaN Epiwafers | Compound Wafer Deliverables
Related Coverage
Silicon Wafer Production Overview | Materials & IP Hub | Crystal Growing | SiC Nine-Market Convergence Spotlight | Critical Elements & Geopolitics | Bottleneck Atlas