Improvement of electrical characteristics and stability of IGZO TFT through surface single crystallization of IGZO film at room temperature

Abstract

The electrical characteristics and stability of indium gallium zinc oxide (IGZO) thin film transistors (TFTs) are improved through surface single crystallization of IGZO film by Cs ions adsorption at room temperature. The experimental results show that the Cs ions can bond with the oxygen ions in IGZO film, changing surface structure of IGZO film from amorphous to a single crystalline. The electrical properties and stability of surface single crystalline IGZO and a-IGZO based thin film transistors were investigated, respectively. With the introduction of the surface single crystalline of the IGZO film, the electrical properties of TFT were greatly improved, showing that the carrier mobility improved from 5.28 cm 2 V −1 s −1 to 8.84 cm 2 V −1 s −1 , and the threshold voltage deceased from 7.6 V to 2.3 V, accompanied with a leakage current below 10 −15 A. The stability of V th shifts in surface single crystalline IGZO based TFT was 6.3 V under V GS =20 V for 5000 s, improved by ∼32% compared with that of a-IGZO TFT.

As-Grown Crystalline InGaZnO by Spray Pyrolysis on a Flexible Substrate for a Thin-Film Transistor with Excellent Stability

“…The comparison of electrical stability of c-IGZO TFT fabricated with various methods is summarized in Table S2 (Supporting Information). 15,18,19,46,48,61,63 Compared with previously reported c-IGZO TFTs, as-grown c-IGZO TFT shows better operational stability. The temperature-dependent transfer curves of c-IGZO TFT measured from 25 to 80 °C are shown in Figure S10a (Supporting Information).…”

“…The metal oxide lattices (M–O), V O , and metal hydroxyl group (M–OH) are deconvoluted at 529.9 ± 0.0 eV, 530.8 ± 0.1 eV, and 531.9 ± 0.1 eV, respectively. , The proportions of M–O, V O , and M–OH in c-IGZO are 84.8%, 10.2%, and 5.0%, respectively, showing higher M–O and very low oxygen-related defects. The result is related to high film density (6.73 g cm –3 ) as a result of the rearrangement of the atoms such as strong In–O bonds with the decrease in vacant sites such as weak In–O bonds during grain growth. , The oxygen-related defects in the c-IGZO films reported in the literature are summarized in Table S1 (Supporting Information). ,,,,− The as-grown c-IGZO by spray pyrolysis is found to have a small concentration of the M–OH group. This can be attributed to the complete evaporation of hydrogen as acetate groups, H 2 O vapor, ammonia (NH 3 ), methane (CH 4 ), and ketene (CH 2 CO) at the substrate temperature of 425 °C. , The impurity concentration in c-IGZO is investigated by XPS analysis.…”

“…The 20 TFTs exhibit an average V TH of −1.00 ± 0.30 V, μ FE of 39.60 ± 4.12 cm 2 V –1 s –1 , μ SAT of 38.20 ± 5.41 cm 2 V –1 s –1 , and SS of 0.21 ± 0.02 V dec –1 . The comparison of c-IGZO TFT performances fabricated with various methods is shown in Table . ,,,,,,,− Excellent electrical performance of as-grown c-IGZO TFT with high mobility results from well-aligned crystalline structure and high mass density. ,, The well-aligned crystalline structure is due to the rearrangement of cations at a high substrate temperature, while the high mass density provides a stable matrix. This can lead to similar mobility to single-crystal IGZO TFTs because it forms a perfect edge-sharing network of InO 6 octahedra to realize a higher mass density and smooth carrier transport path. , In addition, the low resistance of the offset and contact regions in as-grown c-IGZO TFT by the high doping efficiency is another factor for high mobility.…”

“…The low oxygen-related defects (see Table S1, Supporting Information), as well as the well-aligned crystalline structure with high mass density, contribute to the excellent electrical stability. The comparison of electrical stability of c-IGZO TFT fabricated with various methods is summarized in Table S2 (Supporting Information). ,,,,,, Compared with previously reported c-IGZO TFTs, as-grown c-IGZO TFT shows better operational stability. The temperature-dependent transfer curves of c-IGZO TFT measured from 25 to 80 °C are shown in Figure S10a (Supporting Information).…”

Optimizing the Properties of InGaZnOx Thin Film Transistors by Adjusting the Adsorbed Degree of Cs+ Ions

“…The intensity of the diffraction peaks in samples A1 to A4 gradually increased, indicating that the surface crystallization strength of the Cs-IGZO film can be promoted by increasing the degree of adsorption of Cs + ions, thereby obtaining the more regular surface structure of Cs-IGZO films. Since the diffraction peak at a diffraction angle of 33.1° of Cs-IGZO films corresponds to (101) orientation of indium, the XRD results of samples A1 to A4 also indicate that the regular-arranged In atoms are the primary cause of surface crystallization of Cs-IGZO films [23].…”