Plasmonic Silicon-graphene Schottky Photodetector for on-chip Applications in the Telecom Spectral Band

Ilya Goykhman Cambridge Graphene Centre, University of Cambridge, Cambridge, UK Ugo Sassi Cambridge Graphene Centre, University of Cambridge, Cambridge, UK Boris Desiatov Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Domenico De Fazio Cambridge Graphene Centre, University of Cambridge, Cambridge, UK Noa Mazurski Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Joseph Shappir Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Uriel Levy Department of Applied Physics, The Hebrew University of Jerusalem, Jerusalem, Israel Andrea Ferrari Cambridge Graphene Centre, University of Cambridge, Cambridge, UK

Graphene-based photodetectors can have broadband operation [1-5] and ultra-fast response exceeding state-of-the-art semiconductor devices [6]. However, even though graphene absorbs ~2.3% per layer [7], the highest of any two dimensional material, in absolute terms it is still too small for construction of high responsivity photodetectors. Thus many approaches have been developed to increase responsivity, including coupling with localized plasmons [3] or semiconducting [8] nanoparticles. However, other limitations stem from these, such as loss of broad-band operation, or limited speed. Recently, several waveguide integrated graphene-photodetector schemes have been demonstrated, where graphene is evanescently coupled to the waveguide [9]. In this configuration, a longer interaction length between graphene and optical mode enhances absorption and photodetection efficiency, without harming high operation speed and broadband response. Here, we present a self-aligned approach for the fabrication of compact (5mm), surface plasmon polariton (SPP) waveguide-based silicon-graphene Schottky photodetectors for on-chip application in the telecom spectral band. A metal-graphene-silicon interface of SPP waveguide allows internal photoemission process of hot carriers from both metal and graphene to silicon. SPP guiding enables high optical confinement in graphene, which in turn provides enhanced photodetector responsivity ~85mA/W and internal quantum efficiency ~7%. The presented device shows one of the highest responsivity together with the lowest dark current demonstrated so far in graphene based photodetectors for the telecom wavelengths.

Fig. 1. a) Scanning electron micrograph of the fabricated device. b) I-V characteristics and photorespose of the fabricated device.

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ig312@cam.ac.uk