Lin Zhang

Si-based Nanostructures

Nanyang Technological University

School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798

Email: zhang.lin@ntu.edu.sg

Biography

   Dr. Lin Zhang received the B.S. degree in Electrical and Electronic Engineering from Nanyang Technological University Singapore, in 2007, and the Ph.D. degree in Electrical and Electronic Engineering from Nanyang Technological University Singapore, in 2013. He was a Product engineer with TECH Semiconductor Singapore from 2007 to 2009. He is currently a Postdoctoral Researcher with Nanyang Technological University. His research interests include Group-IV materials growth, characterizations, device fabrications for Si photonic applications.

Abstract for Presentation

Tensile Strained GeSn-on-insulator (GSOI) Platform via 2layer

Step-graded GeSn Epitaxial Growth and Direct Wafer Bonding (DWB)

   Epitaxial GeSn films become direct bandgap materials with ~6 to10% of Sn content and/or through strain engineering, which could expend the operating wavelength of group IV photonics into the mid-infrared (MIR) range [1-2]. However, it is very challenging to incorporate Sn into Ge crystal lattice due to the extremely limited solid solubility of Sn and Sn is prone to segregation at higher concentrations [3]. Strain relaxation or tensile strain engineering must be considered so as to incorporate higher Sn content. On the other hand, by inserting an insulator layer as the under-cladding layer, a large refractive index (n) contrast between the core material and the undercladding layer could be realized, which is beneficial for compact on-chip design. We presents a novel method of fabricating wafer-scale (6”) and tensile strained GSOI platform via epitaxial growth of GeSn in a CVD system and DWB technique. Chemical and mechanical polish (CMP) is utilized to achieve an ultra-smooth surface. The 2layer step-graded epitaxial growth of GeSn films using Ge2H6 and SnCl4 as precursors is achieved. DWB is used to transfer the tensile strained GeSn film on to the insulator layer to form the GSOI platform. Figure 1(a) shows the HR-TEM image of the tensile GSOI sample, the GeSn layer is single crystalline. Figure 1(b) shows the RSM (224) mapping of the GSOI sample and confirms the tensile strain in the film is ~0.4%. μ-PL measurements in Figure 1(c) show the tensile GSOI has a single peak at 1,997 nm, this corresponds well to the the Γ-LH transition for a GeSn layer with Sn content of ~4%.

References

[1] Y. Chibane, et al., Appl. Phys. Lett., 107 (2010) 053512.

[2] S. A. Ghetmiri, et al., Appl. Phys. Lett., 105 (2014) 051104.

[3] J. P. Fleurial, et al., Electrochem. Soc., 137, 9 (1990).