Plasmon-enhanced hot electron collection in Au–Ag alloy-based zero-bias silicon NIR photodetectors fabricated via pulsed laser deposition

The plasmonic metal Schottky junction on silicon enables efficient near-infrared (NIR) detection beyond the silicon bandgap via internal photoemission and is compatible with CMOS technology, making it ideal for scalable NIR photodetection applications. By alloying two plasmonic metals, one can modify the optical, structural, and electrical properties to enhance photodetection performance. Here, we demonstrate the fabrication of an Ag–Au alloy/n-Si device using a sequential pulsed laser deposition (PLD) technique, controlling the composition ratio of the alloys to optimize film morphology and electrical response in nanostructured thin metal films. The fabricated Au–Ag alloy/n-Si device enables precise control of the Schottky barrier height, tuned between 0.62 and 0.68 eV. Additionally, this alloying process alters the film morphology, impacting light absorption and optical properties. The Au₃₄Ag₆₆/n-Si alloy sample achieves a maximum responsivity of 22.93 mA/W at 1300 nm and 1.23 mA/W at 1550 nm under zero-bias conditions, showing a 15-fold increase over pure Au samples. This study highlights that alloying plasmonic noble metals offers a means to adjust their work function while simultaneously modifying film topology and optical characteristics. These modifications lead to improved detection performance, paving the way for innovative advancements in photodetection, photovoltaics, sensing technologies, and photochemical applications.