Unbiased Plasmonic-Assisted Integrated Graphene Photodetectors

Abstract

Photonic integrated circuits (PICs) for next-generation optical communication interconnects and all-optical signal processing require efficient (∼A/W) and fast (≥25 Gbs −1 ) light detection at low (<pJbit −1 ) power consumption, in devices compatible with Si processing, so that the monolithic integration of electro-optical materials and electronics can be achieved consistently at the wafer scale. Graphene-based photodetectors can meet these criteria, thanks to their broadband absorption, ultrahigh mobility, ultra-fast electron interactions, and strong photothermoelectric effect. High responsivities (∼ 1 A/W), however, have only been demonstrated in biased configurations, which introduce dark current, noise, and power consumption, while unbiased schemes, with low noise and zero consumption, have remained in the ∼ 0.1 A/W regime. Here, we consider the unbiased asymmetric configuration and show that optimized plasmonic enhanced devices can reach for both transverse-electric and transversemagnetic modes (at λ = 1550 nm), ∼A/W responsivity, and ∼ 100 GHz operation speed at zero power consumption. We validate the model and material parameters by simulating experimental devices and derive analytical expressions for the responsivity. Our comprehensive modeling paves the way for efficient, fast, and versatile optical detection in PICs with zero power consumption.

Terahertz Detection with Graphene FETs: Photothermoelectric and Resistive Self-Mixing Contributions to the Detector Response

“…The behavior is weakly dependent on the value of L ug , as one finds when considering the ratio R̃ V , R S M normalo normalp ( 100 normalG normalH normalz ) / R̃ V , P T E normalo normalp ( 100 normalG normalH normalz ) R̃ V , R S M normalo normalp ( 500 normalG normalH normalz ) / R̃ V , P T E normalo normalp ( 500 normalG normalH normalz ) which yields a value of 2.5 for L ug = 0.3 μm, 3.2 for 0.2 μm, and of 3.8 for 0.1 μm. Interestingly, we also observe such a roll-off with frequency for the BG measurement, which we attribute to the contact doping effect , that leads to the metal-contacted SLG/SLG PTE discussed above. Without this doping effect, one would expect a dominant RSM over the PTE since the Seebeck difference between the ungated and gated channel regions is not altered when a BG voltage is applied globally to the entire graphene channel (see also Supporting Information, S4).…”

“…Our EM wave simulations (see Supporting Information Figure S4) indicate that higher carrier mobility is likely to increase the amount of dissipated THz power in the gated channel region. However, to investigate the change in the final RSM-to-PTE ratio for an increased carrier mobility, the interplay between (i) the increased electronic cooling length, , (ii) the increased Seebeck coefficient, , and (iii) the change in the power dissipation profile (see Figures c and S4a in the Supporting Information) need to be taken into account. The actual RSM-to-PTE ratio in high-mobility G-TeraFETs can be studied using similar methods as presented in this work, where the detectors are fabricated with, e.g., hBN-encapsulated graphene.…”

“…This finding has three implications: (i) it supports the basic validity of the underlying assumptions, (ii) it yields an effective length of 0.3 μm, to which the gated channel region contributes to PTE, and (iii) most importantly, the increasing domination of PTE over RSM for rising radiation frequency is a consequence of the change in the power dissipation profile alongside the graphene channel when the frequency increases. The penetration length Δ L to which the PTE contributes to the detector signal below the gate electrode is closely related to the electronic cooling length L c , ,, which scales sublinearly with the charge carrier mobility and determines the length scale over which the heated carriers (here, the carrier heating mainly occurs place in the antenna gap) cool down to the lattice temperature T L . For our low carrier mobility samples, where the mobility ranges from μ FE,h ≈ 1250 cm 2 /(V s) up to μ FE,e ≈ 1600 cm 2 /(V s), an electronic cooling length of L c,h ≈ 0.35 μm and L c,e ≈ 0.38 μm is predicted from theory .…”

Ultralow-noise Terahertz Detection by p–n Junctions in Gapped Bilayer Graphene

“…These complexities can be largely overcome when using graphene as a material for terahertz detection due to its high electron mobility, gate-tunable carrier density, almost frequency-independent light absorption, and small heat capacitance . Owing to its atomically thin body, graphene is compatible with silicon technology − and thus is well suited for on-chip integrated optoelectronics. − …”