Material gain engineering in GeSn/Ge quantum wells integrated with an Si platform

Abstract

It is shown that compressively strained Ge1−xSnx/Ge quantum wells (QWs) grown on a Ge substrate with 0.1 ≤ x ≤ 0.2 and width of 8 nm ≤ d ≤ 14 nm are a very promising gain medium for lasers integrated with an Si platform. Such QWs are type-I QWs with a direct bandgap and positive transverse electric mode of material gain, i.e. the modal gain. The electronic band structure near the center of Brillouin zone has been calculated for various Ge1−xSnx/Ge QWs with use of the 8-band kp Hamiltonian. To calculate the material gain for these QWs, occupation of the L valley in Ge barriers has been taken into account. It is clearly shown that this occupation has a lot of influence on the material gain in the QWs with low Sn concentrations (Sn < 15%) and is less important for QWs with larger Sn concentration (Sn > 15%). However, for QWs with Sn > 20% the critical thickness of a GeSn layer deposited on a Ge substrate starts to play an important role. Reduction in the QW width shifts up the ground electron subband in the QW and increases occupation of the L valley in the barriers instead of the Γ valley in the QW region.

Growth of Ge1−xSnx Nanowires by Chemical Vapor Deposition via Vapor–Liquid–Solid Mechanism Using GeH4 and SnCl4

“…These latter methods provide a good control for Sn incorporation and the possibility of developing heterostructures with sharp interfaces. However, due to the large lattice mismatch between GeSn and the silicon substrate (>4.2%), the elaboration of 2D films leads to a large number of misfit dislocations at the GeSn/Si interface for thick GeSn layers . Different solutions to avoid these defects have been developed like the “GeSn on insulator”, or the growth of nanowires using the bottom‐up approach via the vapor‐liquid‐solid (VLS) mechanism during the CVD process.…”

“…However, due to the large lattice mismatch between GeSn and the silicon substrate (>4.2%), the elaboration of 2D films leads to a large number of misfit dislocations at the GeSn/ Si interface for thick GeSn layers. [11] Different solutions to avoid these defects have been developed like the "GeSn on insulator", [12,13] or the growth of nanowires using the bottom-up approach via the vapor-liquid-solid (VLS) mechanism during the CVD process. Unfortunately, Sn incorporation in the nanowires is much more difficult to achieve with this technique, thus explaining the small amount of studies about GeSn nanowires grown by CVD-VLS process.…”

Design of direct band gap type I GeSn/Ge quantum dots for mid‐IR light emitters on Si substrate

“…The unstrained Ge 1− x Sn x band gaps at high symmetry points (L and Γ) are given as a function of the Sn composition x by: where i denotes L or Γ point and b i is the corresponding band gap bowing parameter, describing the alloy band gap deviation from linear interpolation between constituent elements band gaps. The direct band gap bowing parameter ( b Γ ) is taken to be 2.2 eV , and b L = 0.26 eV . The minimum of the L and Γ valley can be deduced by adding the corresponding strained band gap value to the valence band maximum.…”

“…On the basis of the historical success of III–V material based light emitters' performance improvement , the exploitation of the carriers confinement degrees offered by low dimensional structures such as quantum dots (QD), quantum wires, and quantum wells may constitute the prospective research direction toward a more efficient low‐cost Si‐based light source for mid‐IR sensing on a Si platform. Accordingly, some advanced structures employing GeSn quantum wells based device active layer were reported . As for GeSn QD, the available few reports were focused on direct growth on Si substrate , SiO 2 matrix , and more recently, on Si nanopillar arrays .…”

Digital Etch Technique for Forming Ultra-Scaled Germanium-Tin (Ge 1−x Sn x ) Fin Structure

“…near- and mid-infrared photodetectors 5–8 . In particular, recent theoretical and experimental studies indicate that strain-free Ge 1− x Sn x becomes a direct bandgap material at a Sn composition of about 6.5% to 11% 9–11 , making it a possible candidate as a gain medium in lasers based on group IV materials 12, 13 . Lasing of a direct bandgap Ge 0.874 Sn 0.126 grown on Si substrates was reported recently 14, 15 .…”