Physics / mechanism
Indium phosphide is a III-V compound semiconductor with a direct bandgap of ~1.34 eV and electron mobility ~5,400 cm²/V·s — roughly 4× silicon. The direct gap enables efficient photon emission and absorption without phonon assistance, making it the substrate of choice for telecom-band (1,310 nm / 1,550 nm) lasers, modulators, and photodetectors. InP HBTs reach ft/fmax above 500 GHz, dominating mm-wave and sub-THz applications. Epitaxial growth is predominantly MOCVD on 4-inch wafers (6-inch emerging). Wafer cost remains 10–20× GaAs; threading dislocations from lattice mismatch constrain heterogeneous integration. State-of-the-art integrated InP photonic chips achieve >100 Gbaud PAM-4 modulation in datacentre transceiver PICs.
Competitive landscape
GaAs competes at lower frequencies and shorter wavelengths; cheaper, more mature 6-inch supply chain but no telecom-band advantage. Silicon photonics (SiPh) addresses the same datacentre transceiver market at far lower cost using CMOS fabs, but requires III-V gain elements — often InP — bonded or grown heterogeneously. GaN owns high-power RF. InP’s defensible moat is monolithic integration of gain + routing + detection at 1.55 µm.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.