Ultra-low-cost broad-band near-infrared silicon photodetectors based on hot electrons

Silicon is at the heart of all of the end-user digital devices such as smart phones, laptops, and wearable technologies. It is the holy grail for the largescale production of semiconductor devices since start of the semiconductor era due to its relatively good electrical, mechanical and chemical properties. Silicon’s mediocre optical properties also make it an acceptable material for energy harvesting and ultraviolet photodetection applications. But its relatively large bandgap (1.12 eV ) makes it infrared blind. So Silicon photodetectors fail to detect infrared light using traditional techniques. Hence, an all-Silicon solution is of interest for low-cost civil applications like telecommunication and imaging. Silicon based Schottky junction is a promising candidate for infrared photodetection. Internal photoemission is the main mechanism of photodetection in the Schottky junctions. Incident photons elevate the kinetic energy of the electrons in the metal so that the energetic electrons can jump over the Schottky barrier or tunnel through it. Carefully designed metal contact of the Schottky junction can, at the same time, give rise to hot electron generation through plasmon resonances. Here we introduce ultra-low-cost broad-band near-infrared Silicon photodetectors with a study over types of metal and nanostructures and fabrication techniques. The devices exhibit photoresponsivity as high as 2 mA/W and 600 µA/W at 1300 nm and 1550 nm wavelengths, and can see beyond 2000 nm wavelengths. Their dark current density is as low as 50 pA/µm2 . Simplicity and scalability of fabrication in this type of structures make them the most cost effective infrared detectors due to lack of expensive fabrication steps such as sub-micron lithography and high temperature epitaxial growth techniques.