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Recent Results on the Road to a SiGe Quantum Cascade Laser

  • Alex Borak (a1), Soichiro Tsujino (a1), Claudiu Falub (a1), Maxi Scheinert (a1), Laurent Diehl (a1), Elizabeth Müller (a1), Hans Sigg (a1), Detlev Grützmacher (a1), Ulf Gennser (a2), Isabelle Sagnes (a2), Stefan Blunier (a3), Thomas Fromherz (a4), Yves Campidelli (a5), Oliver Kermarrec (a5), Daniel Bensahel (a5) and Jerome Faist (a6)...


The primary challenges in implementing a Si based quantum cascade laser are discussed. Intersubband absorption measurements were carried out on a series of modulation doped multiquantum well structures. The spectra were compared to the predictions of a 6 band k.p model, which confirmed the excellent accuracy of the model, and its ability to predict the bandstructures of more complicated cascade structures. A detailed structural analysis demonstrated excellent growth quality, with an interface roughness of < 0.4 nm. Electroluminescence measurements on cascade structures with doped contacts, processed as finger structures and waveguides of various sizes, enabled a quantitative analysis of the active region performance. The upper state lifetime τnr was ∼ 100 fs, leading to a total active region optical gain of ∼ 2 cm−1, a factor of ∼ 10 lower than the estimated total losses due to free carrier absorption. The total emitted power and the linewidth of the intersubband emission saturate above ∼ 6.5 kA/cm2, probably due to misalignment of the injector levels at high biases. The effect of leak currents and interspersed light hole states on the intersubband emission are considered.



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  • EISSN: 1946-4274
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