Strain-compensated Si/Si0.2Ge0.8 quantum cascade structures grown on Si0.5Ge0.5 pseudo-substrates

We present the successful growth by molecular beam epitaxy of strain-compensated Si/Si0.2Ge0.8 quantum cascade structures on Si0.5Ge0.5 pseudo-substrates. Three different samples, containing 3, 15 and 30 repetitions of the active region have been investigated. The active region consists of 14 Si0.2Ge0.8 wells separated by thin Si barriers of thickness in the range of 4-26 Angstrom. The X-ray diffraction patterns of the different structures reveal the excellent reproducibility of the quantum well sequence within the sample and from growth run to growth run. Intersubband electroluminescence, due to a transition between heavy hole states, is observed for all three devices. The spectra exhibit a pronounced peak at about 175 meV close to the intended transition energy. Emission intensities, as well as the voltage applied for a given current density, scale with the number of repetitions. (C) 2002 Published by Elsevier Science B.V.