In this paper, an n-type Si 1−x Ge x /Ge (x 0.85) quantum cascade (QC) structure utilizing a deep Ge quantum well for electrons at the point is proposed. Based on linear interpolation, a conduction band offset at the point in a Si 1−x Ge x /Ge (x 0.85) heterostructure is presented, which is suitable for designing a QC laser. This approach has the advantages of a large conduction band offset at the point, a low lattice mismatch between the Si 1−x Ge x /Ge (x 0.85) active layers and the Si 1−y Ge y (y > x) virtual substrate, a small electron effective mass in the band, simple conduction energy band structures and a simple phonon scattering mechanism in the Ge quantum well. The theory predicts that if high-energy electrons are continuously injected into the band, a quasi-equilibrium distribution of electrons between the and L bands can be reached and held, i.e., electrons with a certain density will be kept in the band. This result is supported by the intervalley scattering experiments. In n-type Si 1−x Ge x /Ge (x 0.85) QC structures, population inversion between the laser's upper and lower levels is demonstrated.

No abstract

No abstract