Silicon Meet Graphene for a New Family of Resonant Cavity Enhanced Photodetectors

In this work we have investigated resonant cavity enhanced (RCE) photodetectors (PDs), exploiting the InternalPhotoemission Effect (IPE) through a Single Layer Graphene (SLG) replacing metals in the Silicon (Si)Schottky junctions, operating at 1550 nm. The SLG/Si Schottky junction is incorporated into a Fabry-Pèrot (F-P)optical microcavity in order to enhance both the graphene absorption and the responsivity. These devices areprovided of high spectral selectivity at the resonance wavelength which can be suitably tuned by changing thelength of the cavity. We get a wavelength-dependent photoresponse with external responsivity ?20 mA/W ina planar FíP microcavity with finesse of 5.4. In addition, in order to increase the finesse of the cavity, andconsequently its responsivity, a new device where the SLG has placed in the middle of a Si-based F-Pmicrocavity has been proposed and theoretically investigated. We have demonstrated that, in a properly designeddevice, a SLG optical absorption, responsivity and finesse of 100%, 0.43 A/W and 172 can be obtained,respectively. Unfortunately, the estimated bandwidth is low due to the planarity of the structure where bothOhmic (Al) and Schottky (SLG) contacts are placed in the same plane. In order to improve the PD bandwidth,we have fabricated and characterized a prototype of a vertical RCE SLG/Si Schottky PD where two contacts areboth placed at the edges of a high-finesse 200nm-thick Si-based microcavity. Thanks to this innovative structurean increase of the responsivity-bandwidth product is expected. The insights included in this work can open thepath for developing of a new family of high-performance photodetectors that can find application in siliconphotonics.