Redefining Responsivity in Graphene-based Schottky Diodes

Graphene has great potential in flexible and rigid optoelectronic devices due to its atomic thickness (and hence flexibility), high conductivity and broadband transparency [1], [2]. Graphene forms a Schottky junction with semiconductor materials, which can be exploited as simple photodiodes [3], [4]. Recently, it was reported that insulated regions in graphene/silicon (G/Si) photodiodes, e.g. regions separated by oxides to allow contacting the graphene, have a significant contribution towards the extracted photocurrent [5], [6]. Based on these findings, we have optimized the design of graphene-based photodiodes. Here, we report on these graphene/silicon Schottky diodes with very high responsivity, including analysis of the spectral “fingerprint”. Scanning photocurrent measurements (SPCM) support our claims as they provide local spatial distributions of photocurrents in the devices. Based on our experiments, we revisit the extraction of responsivity in previous literature, where the insulating regions have been largely ignored when calculating it. This leads to a distinct overestimation of responsivity.