Plasmonics-integrated Ge PIN-photodetectors: efficiency enhancement by Al nanoantennas and plasmon detection

Abstract

The aim of integrating plasmonic functionality with photonic devices is twofold: on the one hand, plasmonic nanoantennas can enhance the functionality of photonic devices and enable their miniaturization. On the other hand, photonic devices can be a part of plasmonic transmission lines and act e.g. as plasmon detectors. Here, we present results on both aspects in a CMOS-compatible device setup using Ge PIN-photodetectors and Al nanostructures. Plasmonic nanoantennas are metallic nanostructures that enable the control and manipulation of optical energy in the visible and near-infrared spectrum and have been proposed as a means to enhance absorption and quantum yields for photovoltaics, to increase spatial resolution for optical microscopes and to enhance the energy efficiency of light-emitting devices. We present experimental results on the enhancement of Ge PIN-photodetector efficiency by Al nanoantennas. In order to investigate plasmon waveguiding and detection, metal grating structures and metal-insulator-metal slot waveguides were fabricated by electron beam lithography in the Al metallization layer of Ge PIN-photodetectors. Photocurrent maps of the devices under local illumination show that plasmons can be optically excited at the grating and are then guided by the slot waveguide towards the Ge PIN-photodetector where they are detected as photocurrent. Using Ge PIN-photodetectors and Al nanostructures as a CMOS-compatible device setup, we show how plasmonic nanostructures can be used for efficiency enhancement of photonic devices and discuss plasmon detection with Ge PIN-photodetectors with possible applications.