Abstract
Innovations in the design of field-effect transistor (FET) devices will be the key to future application development related to ultrathin and low-power device technologies. In order to boost the current semiconductor device industry, new device architectures based on novel materials and system need to be envisioned. Here we report the fabrication of electric double layer field-effect transistors (EDL-FET) with two-dimensional (2D) layers of copper indium selenide (CuIn7Se11) as the channel material and an ionic liquid electrolyte (1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6)) as the gate terminal. We found one order of magnitude improvement in the on-off ratio, a five- to six-times increase in the field-effect mobility, and two orders of magnitude in the improvement in the subthreshold swing for ionic liquid gated devices as compared to silicon dioxide (SiO2) back gates. We also show that the performance of EDL-FETs can be enhanced by operating them under dual (top and back) gate conditions. Our investigations suggest that the performance of CuIn7Se11 FETs can be significantly improved when BMIM-PF6 is used as a top gate material (in both single and dual gate geometry) instead of the conventional dielectric layer of the SiO2 gate. These investigations show the potential of 2D material-based EDL-FETs in developing active components of future electronics needed for low-power applications.
Highlights
Since the discovery of single Molybdenum Disulphide (MoS2 ) layer as an active channel component in field-effect transistors (FETs) [1], research on 2D materials for electronics and optoelectronics has gained massive momentum
On-set voltage was found to be Von ~ −15 V, which differentiates from the on-state of the FET from the off-state of the FET
Hysteresis was observed with the cycling of the back gate voltage, which indicates charge trapping at the CuIn7 Se11 and SiO2 interface and/or defects/trap states in the conduction channel
Summary
Since the discovery of single Molybdenum Disulphide (MoS2 ) layer as an active channel component in field-effect transistors (FETs) [1], research on 2D materials for electronics and optoelectronics has gained massive momentum. The higher capacitance in the EDL yield in higher electrostatic charge carrier doping in the semiconductor channel results in high on-state current and lower threshold and operational voltages It has been shown through other different applications, such as batteries, capacitors, fuel cells, solar cells, and actuators, that ionic liquids have exceptional and stable chemical properties [8,9,10,11,12]. A 2D-layered structure of ternary copper indium selenide (CIS)—CuIn7 Se11 (γ-phase of CIS)—has shown to have excellent electronic and optoelectronic properties with field-effect mobility reaching ~37 cm V−1 s−1 along with photo-responsivity of ~32 A W−1 and a response time ~9 μs [27,28] Most of these materials are investigated in the light of FET-based devices with conventional SiO2 gates. Field-effect mobility (μFE) was estimated from Equation (1): operating the device in a dual gate mode (with BMIM-PF6 /PEO as a top gate and SiO2 as a back gate)
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