Extended Defect Propagation in Highly Tensile-Strained Ge Waveguides

Date

2017-03-26

Authors

Qi, Meng
O'Brien, William A.
Stephenson, Chad A.
Patel, Victor
Cao, Ning
Thibeault, Brian J.
Schowalter, Marco
Rosenauer, Andreas
Protasenko, Vladimir
Xing, Huili Grace

Journal Title

Journal ISSN

Volume Title

Publisher

Multidisciplinary Digital Publishing Institute

Abstract

Tensile-strained Ge is a possible laser material for Si integrated circuits, but reports of lasers using tensile Ge show high threshold current densities and short lifetimes. To study the origins of these shortcomings, Ge ridge waveguides with tensile strain in three dimensions were fabricated using compressive silicon nitride (SiNx) films with up to 2 GPa stress as stress liners. A Raman peak shift of up to 11 cm−1 was observed, corresponding to 3.6% hydrostatic tensile strain for waveguides with a triangular cross-section. Real time degradation in tensile-strained Ge was observed and studied under transmission electron microscopy (TEM). A network of defects, resembling dark line defects, was observed to form and propagate with a speed and density strongly correlated with the local strain extracted from both modeled and measured strain profiles. This degradation suggests highly tensile-strained Ge lasers are likely to have significantly shorter lifetime than similar GaAs or InGaAs quantum well lasers.

Description

Keywords

strained germanium, stress liner, tensile strain, direct bandgap, dark line defects, optical waveguide, stability, silicon photonics, Physics

Citation

Qi, M., O’Brien, W. A., Stephenson, C. A., Patel, V., Cao, N., Thibeault, B. J., Schowalter, M., Rosenauer, A., Protasenko, V., Xing, H. G. & Wistey, M. A. (2017). Extended Defect Propagation in Highly Tensile-Strained Ge Waveguides. Crystals, 7, 157.

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© 2017 The Authors.

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