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摘要
Sol-gel-based amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) have gained widespread attention due to their simple process and low cost. Herein, a-IGZO thin films with In : Ga : Zn = 4 : 1 : 4 were fabricated at 400 degrees C using a sol-gel process, and high-performance a-IGZO TFTs were successfully demonstrated through contact engineering following the guidance of the Schottky-Mott rule, i.e., low work function metals In and Ga with low melting points were employed as contact electrodes. The Ga-contacted and In-contacted devices exhibit superior performance. Specifically, at Vds = 1 V, the performance of Ga-contacted devices and In-contacted devices exhibited an increased from mu FE = 5.67 cm2 V-1 s-1, Vth = 2.19 V, SS = 0.91 V dec-1, and ION/IOFF = 7.9 x 105 in Cr-contacted devices to mu FE = 11.40 cm2 V-1 s-1, Vth = 1.17 V, SS = 0.56 V dec-1, and ION/IOFF = 2.5 x 106 as well as mu FE = 12.67 cm2 V-1 s-1, Vth = 0.17 V, SS = 0.47 V dec-1, and ION/IOFF = 5.4 x 106. Meanwhile, the contact resistance of Ga-contacted a-IGZO TFTs (1088 k omega mu m) and In-contacted a-IGZO TFTs (403 k omega mu m) are much lower than that of Cr-contacted devices (1890 k omega mu m). The improvement of device performance can be attributed to lower metal work function and superior contact interface quality, which can inhibit the Fermi level pinning effect and maximize the performance of N-channel a-IGZO TFTs. Furthermore, both the positive and negative bias stability of the devices with the different contact were systematically studied. At 3600 s for NBS (Vgs = -20 V) and PBS (Vgs = +20 V), the Ga-contacted and In-contacted devices are shifted by -3.5 V and 11.5 V and -3.1 V and 9.1 V, respectively, which are better than the -10.6 V and 17 V of the Cr-contacted ones. These results further confirm that In and Ga can form high-quality interfaces with a-IGZO. Our results demonstrate a simple and effective strategy to fabricate high-performance sol-gel-based a-IGZO TFTs and provide a solid foundation for its practical application. @@@ Using low-melting point metals (In, Ga) as contact electrodes significantly enhances the performance of sol-gel processed a-IGZO TFTs.
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