Direct-gap germanium-tin multiple-quantum-well electro-optical devices on silicon or germanium substrates

摘要

Silicon-based laser diodes, optical amplifiers, electrooptical modulators, and photodetectors in which the active region consists of a pseudomorphic GeSn multiple quantum well stack. Each quantum well is tensile-strained Ge.sub.1-x Sn.sub.x layer sandwiched between compressively strained barriers of Ge.sub.1-y Sn.sub.y with x˜0.1, x y and y˜0.15. The GeSn quantum wells have a strain-induced direct gap for strongly allowed band-to-band transitions in the infrared range. The quantum well stack is grown upon a relaxed SiGeSn alloy buffer portion whose composition is graded up from a lattice match at the silicon substrate interface to a Ge or GeSn composition at buffer's top surface. Doped cladding layers are added, so that the devices have a p-i- n diode structure. The monolithic integrated Column IV devices have a rib waveguide structure, where desired, and operate typically in the 2 to 3 micron wavelength range.