III-V and wide-bandgap compound semiconductor supply chain — InP/GaAs substrates and gallium processing (AXT, Dowa), specialty compound-semi materials (5N Plus), epi wafers and laser-diode chips (IQE, LandMark), SOI and engineered substrates (Soitec), SiC wafers and GaN-on-SiC epitaxy (Wolfspeed), MOCVD growth tools (Veeco, Aixtron), compound-semi foundries (Tower Semiconductor, Win Semi), and RF/photonic IC designers leveraging compound-semi processes (MACOM, Qorvo, Skyworks) — enabling datacenter optical interconnect, high-frequency RF, power electronics, and the ex-China supply alternatives made strategically critical by China's gallium and germanium export controls.