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

• Published in: Applied physics letters 2021-11, Vol.119 (19)
• Main Authors: Wu, Shaoteng, Zhou, Hao, Chen, Qimiao, Zhang, Lin, Lee, Kwang Hong, Bao, Shuyu, Fan, Weijun, Tan, Chuan Seng
• Format: Article
• Language: English
• Subjects: Absorption spectra; Absorptivity; Applied physics; Cut off wavelength; Finite element method; Germanium; Membranes; Metal oxide semiconductors; Photometers; Strain distribution; Tensile strain
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0068849

A divergent microstructure was fabricated by complementary metal–oxide–semiconductor compatible processes on the central region of a Ge p–i–n photodetector to enhance the residual tensile strain. A 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 simulations. The suspended germanium membranes enhance the absorption across the C- and L-bands (1528–1560 and 1561–1620 nm) and extend the cutoff wavelength to ∼1700–1937 nm. The Ge absorption coefficient is enhanced by ∼4.2× to 2951 cm−1 at 1630 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.