High‐Speed, Low‐Voltage, and Environmentally Stable Operation of Electrochemically Gated Zinc Oxide Nanowire Field‐Effect Transistors

Abstract

Single‐crystal, 1D nanostructures are well known for their high mobility electronic transport properties. Oxide‐nanowire field‐effect transistors (FETs) offer both high optical transparency and large mechanical conformability which are essential for flexible and transparent display applications. Whereas the “on‐currents” achieved with nanowire channel transistors are already sufficient to drive active matrix organic light emitting diode (AMOLED) displays; it is shown here that incorporation of electrochemical‐gating (EG) to nanowire electronics reduces the operation voltage to ≤2 V. This opens up new possibilities of realizing flexible, portable, transparent displays that are powered by thin film batteries. A composite solid polymer electrolyte (CSPE) is used to obtain all‐solid‐state FETs with outstanding performance; the field‐effect mobility, on/off current ratio, transconductance, and subthreshold slope of a typical ZnO single‐nanowire transistor are 62 cm2/Vs, 107, 155 μS/μm and 115 mV/dec, respectively. Practical use of such electrochemically‐gated field‐effect transistor (EG FET) devices is supported by their long‐term stability in air. Moreover, due to the good conductivity (≈10−2 S/cm) of the CSPE, sufficiently high switching speed of such EG FETs is attainable; a cut‐off frequency in excess of 100 kHz is measured for in‐plane FETs with large gate‐channel distance of >10 μm. Consequently, operation speeds above MHz can be envisaged for top‐gate transistor geometries with insulator thicknesses of a few hundreds of nanometers. The solid polymer electrolyte developed in this study has great potential in future device fabrication using all‐solution processed and high throughput techniques.

Ink-Jet Printed CMOS Electronics from Oxide Semiconductors

“…[ 22,23 ] Next, the class of polymer electrolyte used shows necessary environmental stability and suffi cient thermal endurance. [ 24,25 ] Furthermore, due to the high capacitance of the electrolytic insulator, the operation voltage is reduced to ≤2 V, making such FETs and logics fully battery compatible. Finally, the rheological parameters of the chosen composite solid polymer electrolyte are ideal for the ink-jet printing; thus, the CSPE constitutes a rare example of an easily-printable high performance gate dielectric.…”

Electric double-layer transistors: a review of recent progress

“…Dasgupta and coworkers prepared ZnO single-nanowirebased, electrochemically gated transistors because of the high mobility and superior electronic transport properties of 1D nanostructure [25]. The electrolyte employed in this work was a composite solid polymer electrolyte (CSPE) which not only controls the transistors performances with low-voltage operation but also enhances mechanical flexibility and high optical transparency.…”

A novel ultra-thin-walled ZnO microtube cavity supporting multiple optical modes for bluish-violet photoluminescence, low-threshold ultraviolet lasing and microfluidic photodegradation

“…ZnO is one of the most intensively studied multifunctional wide-bandgap semiconductors in the past decades for UV light sources, high-speed UV photodetectors, transparent conducting electrodes, field-effect transistors, photocatalysts, chemical sensors, energy harvesting devices and so on. [4][5][6][7][8] It has been acknowledged as a versatile building block for micro/nano-optoelectronic applications. Recently, strong current-driven light emissions from an individual ZnO:Ga microwire with tunable visible colors, analogous to incandescent sources, have been realized, which offer a new possibility for future ZnO-based on-chip light sources via electroluminescence.…”