Suspended germanium membranes photodetector with tunable biaxial tensile strain and location-determined wavelength-selective photoresponsivity

• Main Authors: Wu, Shaoteng, Zhou, Hao, Chen, Qimiao, Zhang, Lin, Lee, Kwang Hong, Bao, Shuyu, Fan, Weijun, Tan, Chuan Seng
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Electrical and electronic engineering::Semiconductors; Germanium; Photodetector
• Online Access: https://hdl.handle.net/10356/153161
• Institution: Nanyang Technological University

A divergent microstructure was fabricated by CMOS compatible processes on the central region of a Ge p i-n photodetector to enhance the residual tensile strain. Tunable biaxial tensile strain of ~0.22-1.01% was achieved by varying the geometrical factors, and it was confirmed by Raman measurements and finite element method (FEM) simulations. The suspended germanium membranes enhance the absorption across the C- and L-band (1,528–1,560 nm and 1,561–1,620 nm) and extend the cutoff wavelength to ~ 1,700-1,937 nm. The Ge absorption coefficient is enhanced by ∼4.2× to 2,951 cm−1 at 1,630 nm which is comparable with that of In0.53Ga0.47As. Furthermore, due to the varying strain distribution on the Ge mesa, each photodetector presents the location-determined wavelength-selective photoresponsivity characteristics. This work offers a promising approach for adjusting the absorption spectra of the photodetector by harnessing geometrically amplified biaxial strain.