Graphene Field-Effect Transistors
The device consists of CVD-grown monolayer graphene transferred onto pre-patterned contacts and passivated with a silicon oxynitride stack. CVD graphene enables graphene production on catalyst foils up to 100mm × 100mm in size, allowing to fill a silicon wafer with a few transfers. Fabrication can be performed on 200-mm wafers, where up to hundreds of chips can fit. Each chip contains several groups of transistors. Within each group, transistors have one common source electrode and each one has an individual drain electrode. All groups share a common gate electrode. Silicon oxynitride passivates the entire surface except the transistor channels and the contact pads. The chips can come either as a diced wafer or wire-bonded to PCB mating with board-to-board connectors. These chips are prepared for biosensing studies using an aqueous electrolyte as the gate.
Several configurations can be produced:
- Chips for biosensing applications, exposing the graphene channel and the common in-plane gate electrode, to apply water or a buffer solution on the gate and on the channels, in multiplex
- Similar to the above, with a continuous-plane metal buried gate (to control graphene doping level)
- Some or all devices can be made fully passivated (insensitive to solution for solid-state applications or as a thermal-drift reference in case of biosensing)
- PCB size: 20mm × 22mm, 24 connected contacts, pitch 0.5mm
- Chip size: 4.5mm
- Transistors present: 20, arranged as 4 groups of 4 and 2 groups of 2
- Graphene channel geometry: 25µm (length) × 75µm (width)
- Geometry parameters can be adapted to user specifications
GFET Electronic Characteristics
- Devices on these chips exhibit the typical characteristics of GFETs: ambipolar I(V) curves, each with a Dirac point.
- In the bottom-gate configuration, mobility values calculated using the Y-function methodology are in the range from 2600 to 5000 cm2/Vs.
The representative data used to determine mobility values are available via Virtual Access.
- Disruptive Devices
- Advanced Integration
Key Enabling Capability
- Devices / Test structures
For a typical biosensing application, compared to other types of biosensor chips, the graphene field-effect transistors offer a much lower limit of detection of biomarkers (DNA or proteins). Wafer-scale production provides several hundred biosensors, which, after appropriate biofunctionalization, are sufficient for a systematic investigation of a large panel of samples. These biosensors can be used with model, clinical, or environmental samples.
Fabrication and characterisation: [DOI: 10.3390/ma13245728]
Biofunctionalization and protein sensing: [DOI: 10.1016/j.apsusc.2019.03.004]
Application to DNA sensing: [DOI: 10.1021/acssensors.8b00344]