Physics / mechanism
Transition metal dichalcogenides (TMDs) are van der Waals layered semiconductors with formula MX₂ (M = Mo, W; X = S, Se, Te). Bulk material is indirect-bandgap; at monolayer thickness (~0.7 nm) they transition to direct bandgap — MoS₂ at ~1.8 eV, WSe2 at ~1.65 eV — enabling strong photoluminescence and electroluminescence absent in bulk. Carrier mobility: MoS₂ monolayer ~200 cm²/V·s (encapsulated, hBN substrate); WSe2 ~300 cm²/V·s. Valley polarization (K/K’ valleys) enables valleytronics. Heterobilayers (MoSe₂/WSe₂) host interlayer excitons with ns-scale lifetimes useful for quantum optics. CVD and MBE growth reaching 4-inch wafer uniformity; dielectric integration with high-κ oxides demonstrated at IMEC and Samsung.
Competitive landscape
Silicon remains dominant for logic; TMDs compete only where ultrathin channel is mandatory (sub-1 nm EOT, sub-5 nm node gate length). GaN/SiC own power and RF. III-V (InGaAs, GaAs) outperform in high-frequency transistors and near-IR photonics. Within 2D materials, graphene leads for RF/analog but lacks bandgap; hBN is purely dielectric. Black phosphorus offers higher hole mobility but degrades in air. TMDs’ niche: monolayer photodetectors, gate-tunable LEDs, and post-Si logic where SOI scaling hits physical limits.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.