Design of SiO2\SiGn\GeSn QDPD for 1550nm operation with High-Gain, Low Dark Current assisted by double Charge Barriers.

The rapidly growing demand for near-infrared (NIR) technologies, particularly around the 1550 nm wavelength, has driven intensive research into advanced photodetectors such as SPADs and QDPDs. Conventional NIR photodetectors commonly rely on III–V materials, such as InGaAs, which suffer from high fabrication costs and incompatibility with silicon-based integrated circuits. SPAD detectors offer high sensitivity but lower quantum efficiency. In this work, an enhanced multilayer SiGeSn quantum dot photodetector (QDPD) architecture is proposed to address these limitations. Each quantum dot consists of a GeSn alloy core surrounded by a SiGe shell, with adjacent dot layers separated by a thin oxide layer. First, the influence of Sn composition and oxide separators on device performance is investigated. Subsequently, two charge-selective barrier layers are introduced above and below the quantum dot layers to effectively suppress dark-current carriers while allowing efficient transport of photogenerated carriers. The positions and thicknesses of these barriers are optimized to achieve optimal device performance. The combination of strong quantum confinement and effective dark-current suppression significantly enhances the photoconductive gain and overall detector performance. Simulation results demonstrate that the optimized design reduces the dark current to only 14% of its original value, while the quantum efficiency increases by a factor of six at a modest Sn concentration of just 5%.