Terahertz responsivity and low-frequency noise in biased silicon field-effect transistors

We report bilayer-graphene field effect transistors operating as THz broadband photodetectors based on plasma-waves excitation. By employing wide-gate geometries or buried gate configurations, we achieve a responsivity~1.2V/W (1.3 mA/W) and a noise equivalent power~2×10 -9 W/√Hz in the 0.29-0.38THz range, in photovoltage and photocurrent mode. The potential of this technology for scalability to higher frequencies and the development of flexible devices makes our approach competitive for a future generation of THz detection systems.Generation and detection of radiation across the far infrared or Terahertz (THz) region of the electromagnetic spectrum is promising for a large variety of strategic applications, 1 ranging from biomedical diagnostics 2 to process and quality control, 3 homeland security 1 and environmental monitoring. 4 Due to its non-ionizing nature, 1 THz radiation can penetrate many commonly used dielectrics, 1 otherwise opaque for visible and mid-infrared light, allowing detection of specific spectroscopic features 5 with a sub-millimeter diffractionlimited resolution. µV/W and operating in photovoltage mode at much higher frequencies (2.5 THz).Here we report THz detectors operating at RT in either photovoltage or photocurrent mode with a significant enhancement of sensitivity and lowered NEPs compared to the state of the art. This is achieved by using either large (1 µm) gate lengths, or buried gate geometries on a bilayer graphene (BLG) FET. We use BLG instead of single layer graphene (SLG) since the modulation of carrier density was proved to be more effective in the former case, 19 allowing a higher responsivity at THz frequencies.The devices are prepared as follows. Flakes are mechanically exfoliated from graphite 24 on an intrinsic Si substrate covered with 300nm SiO 2 . BLGs are selected and identified by a combination of optical microscopy 25 and Raman spectroscopy. 26,27 These are then used to fabricate two sets of FETs (samples A, B). In A, source (S) and drain (D) contacts are patterned by electron beam lithography (EBL) and metal evaporation (5nm Cr /80 nm Au). The S contact is connected to one lobe of a 50° bow-tie antenna, and D to a 3 metal pad. After placement of 35nm HfO 2 by atomic layer deposition (ALD), the other lobe of the antenna is fabricated, and constitutes the FET gate (g). The channel length is L SD = 2.5 m, while the gate length w G =1 m (Fig. 1a). In B, one lobe of a log-periodic circular-toothed antenna is fabricated by EBL and metal evaporation to act as buried gate. After deposition of 35 nm HfO 2 by ALD, S and D electrodes are fabricated.Similar to sample A, S is the second lobe of the antenna, while the drain is a metal line connecting to a bonding pad. The channel length is 2.5 m, its width 7.5 m, while w G = 0.3m (Fig. 1b). A BLG flake is then placed onto the pre-fabricated electrodes by wet transfer. 28 Fig. 2 compares the Raman spectra of the flake prior and after placement onto the electrodes. The "2D" peak shows the characteristic multi-band s...

show abstract

“…architectures, 11 showing fast response times and high responsivities. This approach was also extended 12 to…”

mentioning

confidence: 99%

High performance bilayer-graphene terahertz detectors

Spirito

Coquillat

Bonis

et al. 2014

Applied Physics Letters

168

132

View full text Add to dashboard Cite

show abstract

“…As compared to the thermal THz uncooled detectors, the rectifying ones have a wider dynamic range. Relatively low noise (when being zero biased [13]), small dimensions, and availability of technologies make these detectors favorable for subTHz/THz wave detection. All these rectifying detectors are rather fast (the response time τ ≤ 10 -9 s in Si MOSFET detectors [14], τ ≤ 10 -11 s in GaAs uncooled FETs [15], τ ≤ 10 -11 s in SBDs [16]).…”

Section: -11mentioning

confidence: 99%

“…These detectors will be considered here at zero bias, since the nonzero bias will lead to additional noise in FET detectors almost not improving their NEP [13]. Conventional SBD detectors (e.g., GaAs SBDs) for effective power matching, because of high junction resistance, are forward biased though such biasing leads to an additional 1/f noise.…”

Section: -11mentioning

confidence: 99%

Untitled

2016

Semicond. Phys. Quantum Electron. Optoelectron.

View full text Add to dashboard Cite

Abstract. Performance limits of uncooled unbiased field effect transistors (FETs) and Schottky-barrier diodes (SBDs) as direct detection rectifying terahertz (THz) detectors operating in the broadband regime have been considered in this paper. Some basic extrinsic parasitics and detector-antenna impedance matching were taken into account. It has been concluded that, in dependence on radiation frequency, detector and antenna parameters, the ultimate optical responsivity (ℜ opt ) and optical noise equivalent power (NEP opt ) of FETs in the broadband detection regime can achieve ℜ opt ~ 23 kV/W and NEP opt ~ 1⋅10-12 W/Hz 1/2 , respectively. At low radiation frequency ν in the THz spectral region the NEP opt of SBD detectors can be better by a factor of ~1.75 as compared to that of Si MOSFETs (metal oxide semiconductor FETs) and GaAlN/GaN HFETs (heterojunction FETs) with comparable device impedances.

show abstract

“…[5]. The used hydrodynamic transport model predicts only slight improvement in the subthreshold conditions, which has not been proved by practical measurements due to the other deteriorating noise factors.…”

Section: Introductionmentioning

confidence: 99%

Terahertz responsivity of field-effect transistors under arbitrary biasing conditions

Földesy

2013

Journal of Applied Physics

View full text Add to dashboard Cite

Terahertz responsivity and low-frequency noise in biased silicon field-effect transistors

Cited by 39 publications

References 29 publications

High performance bilayer-graphene terahertz detectors

High performance bilayer-graphene terahertz detectors

Untitled

Terahertz responsivity of field-effect transistors under arbitrary biasing conditions

Contact Info

Product

Resources

About