Design, Fabrication, and Evaluation of Waveguide Structure Using Si/CaF₂ Heterostructure for Near- and Mid- Infrared Silicon Photonics

Near-infrared (λ ∼ 1.2 μm) intersubband electroluminescence in Si/CaF2 quantum cascade structures

“…17) We have also fabricated a slab waveguide with a Si/CaF 2 multilayer structure as its core and successfully observed single-transverse-mode light propagation at a wavelength of 1.55 μm, thereby experimentally demonstrating that it can function as a waveguide material. 18) Furthermore, we have proposed a Si/CaF 2 distributed-feedback QCL and theoretically demonstrated the possibility of a single-longitudinal-mode laser oscillation, which is important for sensing and optical communication applications. 19) The Si/CaF 2 heterostructures as the components of QWs have the following attractive features: [20][21][22][23][24] (1) the large conduction band discontinuity ΔE c (2.3 eV) at the heterointerface, which enables NIR light emission by the intersubband transition of electrons in a Si-QW sandwiched by CaF 2 barrier layers; (2) a similar crystal structure and a small misfit (+0.6% @RT) of CaF 2 to Si, which enables multilayered epitaxial growth using MBE-based crystal growth techniques on silicon substrates; (3) mp of Si and CaF 2 greater than 1400 °C, and a CaF 2 bandgap of 12 eV, which is advantageous for the endurance of active devices with current injection; (4) suppressed intermixing of Si and CaF 2 at the heterointerface because of their different bonding mechanisms (Si: covalent; CaF 2 : ionic), which is advantageous for the multilayered formation of nanometer-thick ultrathin layers.…”