In search of a Si/SiGe THz quantum cascade laser

While electroluminescence has been demonstrated at terahertz frequencies from Si/SiGe quantum cascade emitters, to date no laser has been achieved due to poor vertical confinement of the optical mode. A method of increasing the vertical confinement of the optical mode for a Si/SiGe quantum cascade laser is demonstrated using silicon-on-silicide technology. Such technology is used with epitaxial growth to demonstrate a strain-symmetrised 600 period Si/SiGe quantum cascade interwell emission and the polarisation is used to demonstrate the optical confinement. Electroluminescence is demonstrated at ∼3 THz (∼100 μm) from an interwell quantum cascade emitter structure. Calculated model overlap and waveguide losses for ridge waveguides are comparable to values from GaAs quantum cascade lasers demonstrated at terahertz frequencies.