Hybrid Graphene–Si-Based Nanoscale Vacuum Field Effect Phototransistors

Two-dimensional (2D) hybrid nanoelectronic devices stem from the combination of 2D systems or a mixture of 2D materials themselves, such as graphene, with other well-defined nanostructures interacting with each other in the quantum regime and enabling exceptional characteristics. Here, this paper presents a hybrid photodetection platform consisting of a graphene/Si (Gr/Si) heterojunction in conjunction with nanoscale vacuum electronics based on a graphene/SiO2/Si (GrOS) field effect device. The responsivity of the hybrid platforms based on p-Si and n-Si is fully and finely tunable up to 1.2 and 0.45 A/W, respectively, which correspond to external (internal) quantum efficiencies of 235% (350%) and 88% (132%), respectively. The multiplication gain in the proposed hybrid device originates from the impact ionization initiated by photoinduced carrier injection into the self-induced localized electric field (up to ∼106 V/cm) distributed in a 2DEG region in Si. The electrons travel from the Si edge to graphene via nanoscale air channels. The ON/OFF ratios are in the range of ∼102–105. Therefore, this hybrid photodetection platform is architecturally Si-compatible and thus highly promising for ultrafast, low-power, and tunable optoelectronic applications. Moreover, the overall results demonstrate the impacts of nanoscale spacing air gap (∼100 nm) between graphene and Si that may affect the traditional graphene–Si Schottky characteristic, and the localized graphene work function at the Gr/Si interface of a hybrid device is determined mainly by the graphene work function of the GrOS field effect structure.