IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 61, NO. 9, SEPTEMBER 2014 3223 Area and Energy Efficient High-Performance ZnO Wavy Channel Thin-Film Transistor Amir N. Hanna, Student Member, IEEE, Mohamed T. Ghoneim, Student Member, IEEE, Rabab R. Bahabry, Aftab M. Hussain, Student Member, IEEE, Hossain M. Fahad, Student Member, IEEE, and Muhammad M. Hussain, Senior Member, IEEE Abstract—Increased output current while maintaining low power consumption in thin-film transistors (TFTs) is essential for future generation large-area high-resolution displays. Here, we show wavy channel (WC) architecture in TFT that allows the expansion of the transistor width in the direction perpendicular to the substrate through integrating continuous fin features on the underlying substrate. This architecture enables expanding the TFT width without consuming any additional chip area, thus enabling increased performance while maintaining the real estate integrity. The experimental WCTFTs show a linear increase in output current as a function of number of fins per device resulting in 3.5× increase in output current when compared with planar counterparts that consume the same chip area. The new architecture also allows tuning the threshold voltage as a function of the number of fin features included in the device, as threshold voltage linearly decreased from 6.8 V for planar device to 2.6 V for WC devices with 32 fins. This makes the new architecture more power efficient as lower operation voltages could be used for WC devices compared with planar counterparts. It was also found that field effect mobility linearly increases with the number of fins included in the device, showing almost 1.8× enhancements in the field effect mobility than that of the planar counterparts. This can be attributed to higher electric field in the channel due to the fin architecture and threshold voltage shift. Index Terms—Area efficiency, device width, performance, thin film transistors (TFTs), threshold voltage, wavy. I. I NTRODUCTION S EMICONDUCTOR industries are actively exploring amorphous oxide semiconductors (AOS) as channel mate- rial in thin-film transistors (TFTs) for high resolution display technology as they exhibit high mobility, transparency, low- temperature deposition possibility, and potential integration opportunity on plastic-based flexible substrates [1]–[3]. This is especially the case, as the performance of AOS-based Manuscript received September 10, 2013; revised November 9, 2013, December 29, 2013, January 25, 2014, and March 4, 2014; accepted June 29, 2014. Date of publication August 5, 2014; date of current version August 19, 2014. This work was supported by the King Abdullah University of Science and Technology, Thuwal, Saudi Arabia, through the Office of Competitive Research Funds under Grant CRG-1-2012-HUS-008. The review of this paper was arranged by Editor H.-S. Tae. The authors are with the Integrated Nanotechnology Laboratory, Division of Electrical Engineering, Computer Electrical Mathe- matical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia (e-mail: amir.hanna@kaust.edu.sa; mohamed.ghoneim@kaust.edu.sa; rabab.bahabry@ kaust.edu.sa; aftab.hussain@kaust.edu.sa; hossain.fahad@kaust.edu.sa; muhammadmustafa.hussain@kaust.edu.sa). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TED.2014.2336863 TFTs approach those of the more well-established polycrys- talline silicon [4]. In addition, the recent need for large- area high-resolution displays has inspired research on both material selection as well as device architecture for optimiz- ing performance of oxide-based TFTs [5]. Large-area high- resolution displays require both scaling down of the pixel size to achieve the required resolution, as well as operating the display device at higher switching speeds to achieve seamless display experience. This practice in turn necessitates scaling down the backplane TFT device size as well as searching for materials with higher intrinsic mobility to achieve higher output current and faster switching behavior. This is shown from the transistor output current dependence, under high drain bias I D = W 2 L μ sat C ox (V GS - V T ) 2 (1) where μ sat is the saturation field effect mobility, W is the device width, L is the gate length, and C ox is gate oxide capacitance; V GS and V T are the gate to source bias voltage, and threshold voltage, respectively. While increasing operation voltage, V dd and hence V GS would lead to increased output current, it would equally increase power consumption that is quadratically proportional to operation voltage, P αV 2 dd . This is not desirable for energy efficient applications, such as use of light-emitting diode (LED)-based displays for mobile devices, where power consumption is a key element. Therefore, to opti- mize TFT performance from device architecture perspective, device designs that allow smaller gate length ( L ) or larger device width (W ) need to be explored. New architectures, however, should be compatible with the downscaling trend of TFTs, thus not compromising the real estate integrity. Scaling down TFTs as a method of increasing the output current has been explored by decreasing the TFT gate length ( L ) through nonplanar vertical channel architecture, where L is not limited by lithographic limits. This is usually accomplished using multigate FET device architecture, which is an improvement similar to state-of-the-art CMOS technology [6]. However, it comes at the expense of fabrication cost related requirement of advanced lithographic technique as well as suffering from short-channel effects [7]. We have recently shown the effectiveness of wavy chan- nel (WC) architecture for high-performance transistors and potential usefulness for TFT applications [8]–[10]. Here, we show a new TFT architecture that allows the expansion 0018-9383 © 2014 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.