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

Abstract

A clear electroluminescence (EL) from a Si/CaF2 quantum cascade structure has been successfully observed. The structure was equipped with 15 periods of an active region comprising of Si/CaF2 multi-quantum wells and a waveguide grown on the silicon-on-insulator (SOI) substrate by molecular beam epitaxy-based technique. As a result of an optical spectrum measurement by Fourier transform infrared (FTIR) spectroscopy, a clear EL spectrum with a peak at λ ~ 1.2 μm was observed. The EL spectrum is reasonably explained by fitting it with a Lorentzian model that considers the thickness fluctuation of a single monoatomic layer of a Si quantum well, the intra- and inter-subband scattering times, and the carrier escape time. These results indicate that the EL was generated by intersubband transitions in the Si quantum well.