Comprehensive Investigation of GeSn Metasurface Photodetector for Short-Wave Infrared Application

The metasurface structure can effectively manipulate the direction of light propagation, making it highly promising for the development of high-performance photonic devices. GeSn alloy, which is compatible with CMOS processes, is a highly attractive infrared semiconductor. In this study, GeSn metasurface photodetectors (PDs) were fabricated and comprehensively investigated. Optical field distribution simulations at a 2 μm wavelength revealed that the optimized metasurface structure significantly enhances the quantum efficiency (QE) of GeSn PDs by converting light propagation from the longitudinal to the transverse direction. The dark current of the fabricated GeSn metasurface PDs remained nearly unchanged, while the responsivity increased significantly. At a wavelength of 2000 nm, the room-temperature responsivity was improved from 0.10 to 0.34 A/W, and both temperature-dependent and incident light power-dependent responsivities were studied. The cutoff wavelength of the PD was extended from 2750 to 2950 nm due to the enhanced interaction between the light and the GeSn layer. In the tested photocurrent spectrum between 1600 and 2400 nm, the maximum response enhancement factor reached approximately 2 to 4. The significantly enhanced optoelectronic performance indicates that the proposed metasurface structure has great potential for fabricating GeSn PDs operating in the short-wave infrared (SWIR) region.