Tunable Optical Gap at a Fixed Lattice Constant in Group-IV Semiconductor Alloys

Abstract

A direct absorption edge tunable between 0.8 and approximately 1.4 eV is demonstrated in strain-free ternary Ge_{1-x-y}Si_{x}Sn_{y} alloys epitaxially grown on Ge-buffered Si. This decoupling of electronic structure and lattice parameter-unprecedented in group-IV alloys-opens up new possibilities in silicon photonics, particularly in the field of photovoltaics. The compositional dependence of the direct band gap in Ge_{1-x-y}Si_{x}Sn_{y} exhibits a nonmonotonic behavior that is explained in terms of coexisting small and giant bowing parameters in the two-dimensional compositional space.

E centers in ternary Si1−x−yGexSny random alloys

“…This is consistent with previous work for Si 1−x−y Ge x Sn y in which ⌬␣ is zero when the Sn:Si content ratio is 0.266. 3 Since we have considered an Sn:Si content ratio of 0.333, the lattice parameter should have a positive bowing as predicted.…”

“…[1][2][3][4][5][6][7][8] For example, Ga 1−x In x As y quantum wells have been fabricated on lattice matched Ge 1−x Sn x buffer layers. 1 Recently, Bauer et al 9,10 have managed to synthesize single-phase monocrystalline Si 1−x−y Ge x Sn y alloys with a Si content of up to 32% and a Sn content of up to 10%.…”

Direct gap Ge1-ySny alloys: Fabrication and design of mid-IR photodiodes

“…9, and for the ternary Ge 1-x-y Si x Sn y we also used a quadratic polynomial with a bowing parameter b SiSn ¼ 14 eV. 33 For the deformation potentials, we used the values recommended in Refs. 29 and 34.…”

Compositional dependence of the band-gap of Ge1−x−ySixSny alloys

“…For the band-gaps of the constituent materials Si, Ge, and Sn as well as the SiGe bowing parameter, we followed D'Costa et al and used the values 4:1 eV; 0:8 eV, À0:41 eV, and 0:21 eV, respectively. 11,14 For the GeSn bowing parameters, several values can be found in the literature varying between 1:94 eV and 2:61 eV. 11,31 Here, we use the value of 2:46 eV.…”