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Title: Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature

Abstract

The authors report on transparent thin-film transistors using amorphous indium zinc oxides for an active channel layer and gate-source-drain electrodes fabricated by rf magnetron sputtering at room temperature. The conducting properties of the amorphous indium zinc oxides were controlled by oxygen partial pressures in the sputtering ambient. An amorphous AlO{sub x} served as the gate dielectric oxide. Devices were realized that display a threshold voltage of 1.1 V and an on/off ratio of {approx}10{sup 6} operated as a n-type enhancement mode with saturation mobility of 0.53 cm{sup 2}/V s. The devices showed optical transmittance about 80% in the visible range.

Authors:
; ; ; ; ; ; ;  [1];  [2];  [2]
  1. Department of Inorganic Materials Engineering, Kyungpook National University, Daegu 702-701 (Korea, Republic of)
  2. (Korea, Republic of)
Publication Date:
OSTI Identifier:
20883268
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 2; Other Information: DOI: 10.1063/1.2430917; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AMORPHOUS STATE; CARRIER MOBILITY; DEPOSITION; DIELECTRIC MATERIALS; ELECTRIC POTENTIAL; ELECTRODES; INDIUM COMPOUNDS; LAYERS; OPACITY; OXYGEN; PARTIAL PRESSURE; SEMICONDUCTOR MATERIALS; SPUTTERING; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; TRANSISTORS; ZINC OXIDES

Citation Formats

Song, Ju-Il, Park, Jae-Soung, Kim, Howoon, Heo, Young-Woo, Lee, Joon-Hyung, Kim, Jeong-Joo, Kim, G. M., Choi, Byeong Dae, School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, and Display and Nano Devices Laboratory, Daegu Gyeongbuk Institute of Science and Technology, Daegu 704-230. Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature. United States: N. p., 2007. Web. doi:10.1063/1.2430917.
Song, Ju-Il, Park, Jae-Soung, Kim, Howoon, Heo, Young-Woo, Lee, Joon-Hyung, Kim, Jeong-Joo, Kim, G. M., Choi, Byeong Dae, School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, & Display and Nano Devices Laboratory, Daegu Gyeongbuk Institute of Science and Technology, Daegu 704-230. Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature. United States. doi:10.1063/1.2430917.
Song, Ju-Il, Park, Jae-Soung, Kim, Howoon, Heo, Young-Woo, Lee, Joon-Hyung, Kim, Jeong-Joo, Kim, G. M., Choi, Byeong Dae, School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, and Display and Nano Devices Laboratory, Daegu Gyeongbuk Institute of Science and Technology, Daegu 704-230. Mon . "Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature". United States. doi:10.1063/1.2430917.
@article{osti_20883268,
title = {Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature},
author = {Song, Ju-Il and Park, Jae-Soung and Kim, Howoon and Heo, Young-Woo and Lee, Joon-Hyung and Kim, Jeong-Joo and Kim, G. M. and Choi, Byeong Dae and School of Mechanical Engineering, Kyungpook National University, Daegu 702-701 and Display and Nano Devices Laboratory, Daegu Gyeongbuk Institute of Science and Technology, Daegu 704-230},
abstractNote = {The authors report on transparent thin-film transistors using amorphous indium zinc oxides for an active channel layer and gate-source-drain electrodes fabricated by rf magnetron sputtering at room temperature. The conducting properties of the amorphous indium zinc oxides were controlled by oxygen partial pressures in the sputtering ambient. An amorphous AlO{sub x} served as the gate dielectric oxide. Devices were realized that display a threshold voltage of 1.1 V and an on/off ratio of {approx}10{sup 6} operated as a n-type enhancement mode with saturation mobility of 0.53 cm{sup 2}/V s. The devices showed optical transmittance about 80% in the visible range.},
doi = {10.1063/1.2430917},
journal = {Applied Physics Letters},
number = 2,
volume = 90,
place = {United States},
year = {Mon Jan 08 00:00:00 EST 2007},
month = {Mon Jan 08 00:00:00 EST 2007}
}
  • Depletion-mode indium zinc oxide (IZO) channel thin film transistors were fabricated on glass substrates from layers deposited at room temperature using rf magnetron sputtering. The threshold voltage was in the range from -5.5 to -6.5 V depending on gate dielectric (SiO{sub 2}) thickness and the drain current on-to-off ratio was {approx}10{sup 5}. The maximum field effect mobility in the channel was {approx}4.5 cm{sup 2} V{sup -1} s{sup -1}, lower than the Hall mobility of {approx}17 cm{sup 2} V{sup -1} s{sup -1} in the same layers, suggesting a strong influence of scattering due to trapped charges at the SiO{sub 2}-IZO interface.more » The low deposition and processing temperatures make these devices suitable for applications requiring flexible substrates.« less
  • We report on the generation and characterization of a hump in the transfer characteristics of amorphous indium gallium zinc-oxide thin-film transistors by positive bias temperature stress. The hump depends strongly on the gate bias stress at 100 °C. Due to the hump, the positive shift of the transfer characteristic in deep depletion is always smaller that in accumulation. Since, the latter shift is twice the former, with very good correlation, we conclude that the effect is due to creation of a double acceptor, likely to be a cation vacancy. Our results indicate that these defects are located near the gate insulator/activemore » layer interface, rather than in the bulk. Migration of donor defects from the interface towards the bulk may also occur under PBST at 100 °C.« less
  • We report an investigation of the effects of low-temperature annealing on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). X-ray photoelectron spectroscopy was used to characterize the charge carrier concentration, which is related to the density of oxygen vacancies. The field-effect mobility was found to decrease as a function of the charge carrier concentration, owing to the presence of band-tail states. By employing the transmission line method, we show that the contact resistance did not significantly contribute to the changes in device performance after annealing. In addition, using low-frequency noise analyses, we found that themore » trap density decreased by a factor of 10 following annealing at 120 °C. The switching operation and on/off ratio of the a-IGZO TFTs improved considerably after low-temperature annealing.« less
  • High-performance amorphous ({alpha}-) InGaZnO-based thin film transistors (TFTs) were fabricated on flexible polyethylene terephthalate substrates coated with indium oxide (In{sub 2}O{sub 3}) films. The InGaZnO films were deposited by rf magnetron sputtering with the presence of O{sub 2} at room temperature. The n-type carrier concentration of InGaZnO film was {approx}2x10{sup 17} cm{sup -3}. The bottom-gate-type TFTs with SiO{sub 2} or SiN{sub x} gate dielectric operated in enhancement mode with good electrical characteristics: saturation mobility 11.5 cm{sup 2} V{sup -1} s{sup -1} for SiO{sub 2} and 12.1 cm{sup 2} V{sup -1} s{sup -1} for SiN{sub x} gate dielectrics and drain currentmore » on-to-off ratio >10{sup 5}. TFTs with SiN{sub x} gate dielectric exhibited better performance than those with SiO{sub 2}. This is attributed to the relatively high dielectric constant (i.e., high-k material) of SiN{sub x}. After more than 500 h aging time at room temperature, the saturation mobility of the TFTs with SiO{sub 2} gate dielectric was comparable to the as-fabricated value and the threshold voltage shift was 150 mV.« less
  • We have studied the effect of long time post-fabrication annealing on negative bias illumination stress (NBIS) of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Annealing for 100 h at 250 °C increased the field effect mobility from 14.7 cm{sup 2}/V s to 17.9 cm{sup 2}/V s and reduced the NBIS instability remarkably. Using X-ray photoelectron spectroscopy, the oxygen vacancy and OH were found to exist at the interfaces of a-IGZO with top and bottom SiO{sub 2}. Long time annealing helps to decrease the vacancy concentration and increase the metal-oxygen bonds at the interfaces; this leads to increase in the free carrier concentrations in a-IGZO and field-effect mobility.more » X-ray reflectivity measurement indicated the increment of a-IGZO film density of 5.63 g cm{sup −3} to 5.83 g cm{sup −3} (3.4% increase) by 100 h annealing at 250 °C. The increase in film density reveals the decrease of O vacancy concentration and reduction of weak metal-oxygen bonds in a-IGZO, which substantially helps to improve the NBIS stability.« less