Photoluminescence properties of heavily Sb doped Ge_1−x Sn _x and heterostructure design favorable for n⁺-Ge_1−x Sn _x active layer

Abstract

We investigated the photoluminescence (PL) properties of heavily Sb doped n+-Ge1−x Sn x layers and demonstrated the formation of a double heterostructure (DHS) for the n+-Ge1−x Sn x active layer. A single PL peak was observed for n+-Ge1−x Sn x layers thicker than 80 nm with increasing the Sb concentration up to 1020 cm−3, attributed to the superior crystallinity and pseudo-direct bandgap transition mechanism, while a 15 nm thick n+-Ge1−x Sn x layer did not exhibit PL signals. A favorable heterostructure for n+-Ge1−x Sn x is proposed from the viewpoint of the increased valence band offset (ΔE v) using n-Si y Ge1−y as the cladding layer. We demonstrated the formation of an n-Si y Ge1−y (15 nm)/n+-Ge1−x Sn x (15 nm)/n-Si y Ge1−y (15 nm) DHS with a superior crystallinity and high PL peak intensity comparable to that of a thick n+-Ge1−x Sn x . We discuss the reasons for the PL performance improvement by forming the DHS, including the sufficient carrier confinement and the suppression of surface recombination.

Self-organized Ge1−x Sn x quantum dots formed on insulators and their room temperature photoluminescence

“…This suggests the carrier confinement and/or the defect termination of Ge 1−x Sn x QDs surface by SiO 2 layer is important to cause the PL emission of the Ge 1−x Sn x QDs as so far reported. 2) Next, we performed PDA for some samples. Figure 8(b) shows the PL spectra of the prepared samples with T PDA of 300 °C-500 °C measured at RT.…”

“…1) However, the E gΓ of the direct transition Ge 1−x Sn x bulk is less than 0.6 eV. To achieve luminescence preferable for the optical interconnect of LSIs, using quantum levels formed by lowering the dimensions of the light-emitting layers such as multi-quantum-wells (MQWs), 2,3) nanowires, 4,5) and QDs [6][7][8] is a feasible approach to realizing high E gΓ . Light sources based on high-density (>10 10 cm −2 ) QDs are particularly promising because of their lower power consumption and greater operational temperature stability compared to MQWs.…”