An n-type SiGe/Ge QC structure utilizing the deep Ge quantum well for electron at the Γ point

Abstract

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.

Material configurations forn-type silicon-based terahertz quantum cascade lasers

“…13 However, a range of alternative material configurations have been considered in recent years. L valley transitions in (001) oriented Ge/GeSi have attracted greatest attention, [14][15][16] although transitions in the ∆ valleys of (111) oriented Si/SiGe, 17,18 the Γ valley of Ge/GeSi, 19 and the L valleys of Ge/GeSiSn 20 have also been considered.…”

Intersubband carrier scattering inn- andp−Si∕SiGequantum wells with diffuse interfaces

“…3,4 A quantum cascade laser (QCL) has not yet been developed in Si/Si 1−x Ge x although several designs have been proposed recently. 5,6 In order to accurately design and simulate such structures, a good understanding of intersubband carrier dynamics is required. Previous models have assumed that interfaces between layers are perfectly abrupt, 7 while in reality, diffuse Ge profiles may result either by design, by interdiffusion during the growth process or by surface segregation of Ge atoms.…”

Theory and design of quantum cascade lasers in (111)n-type Si/SiGe

“…5 The high longitudinal effective mass of SiGe ∆ valleys is commonly regarded as a major obstacle to n-type QCLs, 6 and recent theoretical investigations have used transitions in the Γ and L valleys instead. 7,8 We have however shown previously that a (111) oriented Si/SiGe QCL using ∆ valley transition is viable. 9 In this paper, we compare the strain tensors for (001) and (111) oriented layers.…”

“…7,8 We have however shown previously that a (111) oriented Si/SiGe QCL using ∆ valley transition is viable. 9 In this paper, we compare the strain tensors for (001) and (111) oriented layers.…”