Enhancing Extended SWIR Al_0.3InAsSb PIN Photodetectors with All-Dielectric Amorphous Germanium Photon-Capturing Gratings

The extended short-wavelength infrared (eSWIR) spectrum, spanning from 1.9 to 2.2 μm, plays a pivotal role in many civil and military applications. Consequently, there is a consistent demand for high-performance eSWIR photonic devices, such as photodetectors, to drive technological advancements This study explores improving the absorption efficiency of Al_0.3InAsSb PIN photodetectors at the critical 2 μm wavelength. Our research highlights the potential of amorphous germanium (a-Ge), a transparent dielectric material with a high refractive index, in enhancing the performance of eSWIR photodetectors. We report an 113% experimental improvement in quantum efficiency for a digital alloy Al_0.3InAsSb PIN photodetector by employing an all-dielectric photon-capturing structure composed of one-dimensional (1D) a-Ge gratings. Our simulations reveal that the 1D a-Ge grating effectively confines electromagnetic fields within the absorption layer and significantly reduces reflection.