Abstract
This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing.
Highlights
Zinc oxide thin-film transistors are receiving increasing attention because high values of field-effect mobility (3 to 15 cm2/Vs) can routinely be achieved in layers deposited at low temperature (
A variety of approaches have been used for the lowtemperature deposition of ZnO-based materials, including sputtering [4,5,6], pulsed laser deposition [7], solutionbased processes [8], and atomic layer deposition (ALD) [1,2,3,9,10,11,12]
ALD ZnO layers with reasonable electrical and optical properties can be obtained at deposition temperatures below 100°C [13] and even down to room temperature [14,15]
Summary
Zinc oxide thin-film transistors are receiving increasing attention because high values of field-effect mobility (3 to 15 cm2/Vs) can routinely be achieved in layers deposited at low temperature (
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