Modulation of light absorption in flexible GeSn metal–semiconductor–metal photodetectors by mechanical bending

• Main Authors: An, Shu, Wu, Shaoteng, Tan, Chuan Seng, Chang, Guo-En, Gong, Xiao, Kim, Munho
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics; Dark Currents; Light Absorption
• Online Access: https://hdl.handle.net/10356/153649
• Institution: Nanyang Technological University

We have demonstrated flexible GeSn metal–semiconductor–metal (MSM) photodetectors (PDs) by exploring the effect of mechanical strain on their optoelectronic properties. The PDs were fabricated from transfer-printed GeSn nanomembranes on polyethylene terephthalate (PET) substrates. Strain was introduced into the GeSn PDs under bend-down (uniaxial tensile strain) and bend-up (uniaxial compressive strain) conditions and their values were measured by Raman spectroscopy. The applied strain can affect the band-structure of the GeSn alloys, leading to a modulation of the electrical and optical characteristics of the PDs. Accordingly, dark current characteristics show an increase from 8.1 to 10.3 μA under the bend-down conditions and a decrease to 7.2 μA under the bend-up conditions, respectively. The optical responsivity at a wavelength of 2 μm increased by 151% under bend-down conditions, while it decreases by 35% under bend-up conditions. A theoretical study was carried out to support the fact that the responsivity enhancement is attributed to the change in the absorption coefficient of the strained GeSn. The results offer a new pathway to modulate the optical properties of GeSn for flexible applications.