Physics / mechanism
Compound semiconductors are crystalline materials formed from two or more elements, typically III-V (GaAs, InP, GaN, InAs) or II-VI (CdTe, ZnSe) combinations. Unlike silicon, their direct bandgaps enable efficient photon emission and absorption; high electron mobility (GaAs ~8500 cm²/V·s vs Si ~1400) enables fast switching at lower voltages. Key parameters: bandgap tunability (0.17–3.4 eV across III-Vs), breakdown field (GaN ~3.3 MV/cm), lattice constant matching for epitaxial stack design. State of the art: 8-inch GaN-on-Si for power, InP-based PICs operating at 400G+, GaAs in 5G PA modules at >40% PAE. MOCVD and MBE dominate deposition; wafer costs remain 5–20× silicon equivalents.
Competitive landscape
Silicon dominates logic and commodity analog but fails above ~1 keV RF frequencies, at high junction temperatures, and in photonic applications requiring direct bandgap. SiC competes with GaN in power switching (higher blocking voltage, better thermal conductivity, but lower frequency ceiling). Silicon photonics (SiPh) competes in datacom PICs via CMOS-compatible fab but struggles with efficient light emission and requires III-V heterogeneous integration for lasers. GaAs retains dominance in mobile PAs; InP leads coherent optical. Diamond and Ga₂O₃ are emerging ultra-wide-bandgap challengers, still pre-commercial.
| Material | Key strength | Key weakness |
|---|---|---|
| GaN | RF + power, high temp | Substrate cost, defect density |
| InP | Coherent photonics, high-freq | Fragile, expensive, small wafers |
| SiC | Power, rugged | Limited RF, slower switching vs GaN |
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.