Highly Stable Thin-Film Transistors based on Indium Oxynitride

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Functional Inorganic Materials and Devices

Highly Stable Thin-Film Transistors based on Indium Oxynitride Semiconductor Hyoung-Do Kim, Jong Heon Kim, Kyung Park, Yun Chang Park, Sunkook Kim, Yong Joo Kim, Jozeph Park, and Hyun-Suk Kim ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b02678 • Publication Date (Web): 18 Apr 2018 Downloaded from http://pubs.acs.org on April 18, 2018

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ACS Applied Materials & Interfaces

Highly Stable Thin-Film Transistors based on Indium Oxynitride Semiconductor Hyoung-Do Kim1, Jong Heon Kim1, Kyung Park2, Yun Chang Park3, Sunkook Kim4, Yong Joo Kim5*, Jozeph Park6* and Hyun-Suk Kim1*

1

Department of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Republic of Korea

2

School of Integrated Technology, Yonsei University, Incheon 21983, Republic of Korea

3

National Nano Fab Center, Daejeon 305-806, Republic of Korea.

4

School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 16419, Republic of Korea

5

Biosystems Machinery Engineering, Chungnam National University, Daejeon 34134, Republic of Korea

6

Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea

Abstract In this study, the properties of indium oxynitride (InON) semiconductor films grown by reactive radio frequency sputtering were examined both experimentally and theoretically. Also, thin film transistors (TFTs) incorporating InON as the active layer were evaluated for the first time. It is found that InON films exhibit high stability upon prolonged exposure to air, and the corresponding TFTs are more stable when subjected to negative bias illumination stress (NBIS), compared to devices based on indium oxide (In2O3) or zinc oxynitride (ZnON) semiconductors. X-ray photoelectron spectroscopy (XPS) analyses of the oxygen 1s peaks suggest that as nitrogen is incorporated into In2O3 to form InON, the relative fraction of oxygen deficient regions decreases significantly, which is most likely to occur by having the valence band maximum (VBM) shifted up. Density functional theory (DFT) calculations indicate that the formation energy of InN is much lower than Zn3N2, thus accounting for the higher stability of InON compared to ZnON in air.

Keywords: Indium oxynitride (InON), thin film transistor; negative bias illumination stress 1

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(NBIS), air Stability, density functional theory (DFT), first principle calculation.

Introduction Increasing demands for cost effective switching or driving transistors in the flat panel display industry have led to the development of metal oxide semiconductors such as In-GaZn-O (IGZO)1-3. Thin-film transistors (TFT) that incorporate such materials exhibit field effect mobility near 10 cm2/Vs, and are suitable for the fabrication of large size liquid crystal display (LCD) or active matrix light emitting diode (AMOLED) panels4. However, most oxide semiconductors inevitably contain oxygen-related defects such as oxygen vacancies (VOs) that may induce stability issues under bias stress and illumination5. Recent studies on a relatively novel type of semiconductor, zinc oxynitride (ZnON)68

, have shown that high mobility semiconductor films may be obtained by reactively

sputtering a Zn metal target, which involves a simple and inexpensive process. The optimization of the associated TFT properties usually consists of controlling the nitrogen to oxygen anion ratio8 or thermally annealing the ZnON layer9, in order to obtain sufficiently low leakage current levels while preserving high field effect mobility. TFTs based on ZnON exhibit good stability with respect to illumination, with negligible persistent photoconduction (PPC) effects. The PPC phenomenon in oxide semiconductors is suggested to occur mainly by the oxygen deficient sites that prevent the spontaneous recombination of photo-generated electrons and holes after removing the light source. However the incorporation of nitrogen in zinc oxide (ZnO) to produce N-rich ZnON was shown to result in fast recombination of the photo-induced carriers, drastically reducing the PPC effect6. It is suggested that the incorporation of abundant nitrogen into ZnO shifts the valence band maximum (VBM) upwards, thus passivating the oxygen-related defects that lie close to the initial VBM. Despite the high electron mobility, N-rich ZnON is generally unstable when exposed to air ambient conditions and easily oxidizes into ZnO. Here, the relatively weak Zn-N bonds readily convert to Zn-O bonds, therefore capping layers must be formed by thermal annealing8 or plasma treatment10 in order to prevent the evaporation of nitrogen. The present work consists of a study on a similar type of material, indium oxynitride (InON), which is often used for optoelectronic applications11-13 and also exhibits higher stability with respect to air exposure. TFTs incorporating this semiconductor exhibit reasonable switching 2


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characteristics and reliability under bias stress, and first principles calculations indicate that In-N bonds are stronger than Zn-N bonds, thus accounting for the higher durability when exposed to air.

Experimental Section All computations were performed by first principles density functional theory (DFT) calculations using the generalized gradient approximation (GGA)14 for the exchangecorrelation potential proposed by Perdew, Burke, and Ernzerhof. Vienna Ab initio Simulations Package (VASP) code15, employing a plane-wave basis set with an energy cutoff of 400 eV, within the projector augmented-wave (PAW) approach16. In this work, the 80-atom conventional cell for Zn3N2 and the 72-atom supercell for InN were used in the formation energy calculation. The Brillouin zone was sampled with 2×2×2 k-points sampling. In2O3, InON, and InN films were deposited on glass substrates by radio frequency (RF) reactive-sputtering using an In metal target. The applied RF power fixed at 25 W, and the reactive gas flow rate ratio was Ar:O2:N2 = 10:2.0:0 (In2O3), 10:0.6:20 (InON), 10:0:20 (InN) respectively. The crystal structures of all thin-films were examined by grazing incidence angle X-ray diffraction (GIAXRD) using a Cu Kα radiation (Rigaku, D/MAX2500). Also, X-ray photoelectron spectroscopy (XPS) was carried out to observe the chemical bonding states of nitrogen and oxygen components, using a monochromatic Al Kα X-ray source. Before analyses, the surface of each film was sputtered with a low energy Ar+ ion beam (200 eV) for 30 s to eliminate contaminations. The peak position was calibrated with respect to the C 1s peak, of which the standard binding energy is about 284.5 eV. TFT devices using In2O3, InON, and InN active layers were fabricated on highly doped p-type Si substrates with thermally grown 100 nm-thick SiO2 gate dielectrics. The semiconductor islands were patterned using shadow masks. After thermal annealing at 300 °C for 1 hour in air, 150 nm-thick indium tin oxide (ITO) layers were deposited to form the source-drain electrodes (applied RF power: 50 W, Ar gas flow rate: 18 sccm), also using shadow masks. No intentional substrate heating was carried out during all sputter deposition processes, and the increase in substrate temperature during film growth is believed to have minor influence on the final device properties. The transfer characteristics of the devices with width / length = 800 µm / 200 µm were collected using a HP 4156B semiconductor parameter 3



analyzer in a dark room under ambient conditions. The threshold voltage (VTH), subthreshold swing (S.S.), and field effect mobility (µ FE) parameters were extracted in compliance with the gradual channel approximation17. The field effect mobility was extracted in the linear and saturation regime with the drain voltage (Vd) fixed at 0.1 and 10 V, respectively. The devices were then subjected to positive bias stress (PBS) and negative bias and illumination stress (NBS, NBIS), with VG = 20 V (PBS), -20 V (NBS, NBIS) and VD = 0.1 V. A light source with a luminance of 1500 lux was used to illuminate the devices from the top. Each stress experiment was conducted at room temperature for a total duration of 1 hour.

Results and discussion The electrical properties of In2O3, InON, and InN layers were compared through Hall measurements and 4-probe analyses. Table 1 shows the Hall mobility, carrier concentration and sheet resistance of each film. The resistivity of In2O3 is beyond the measurement limits of the instruments. InN is well known to be a narrow band-gap material (Eg = 0.7 ~ 1.5)18-20, and the measured data reflect its conductive nature (Ne > 1020 cm-3). The Hall mobility of InN is rather low (11.0 cm2V-1s-1), which is highly likely to originate from the scattering between individual carriers. In contrast, InON has a relatively low carrier concentration and high Hall mobility, which suggests that it is more suitable as the active layer of a thin film transistor, so that the device easily turns off when needed and provides high current levels in its ON state. To analyze the microstructure of In2O3, InON, and InN films, grazing incidence angle X-ray diffraction (GIAXRD) was carried out. The XRD patterns of each layer are shown in figure 1. InN consists of a polycrystalline structure that exhibits a major InN (002) peak and a minor InN (103) peak. A polycrystalline structure is also observed in the In2O3 diffractogram, where an In2O3 (222) and an In2O3 (400) peak are observed. However, InON appears to be composed mainly of an amorphous matrix, which may originate from a relatively large difference in lattice structure between cubic In2O3 and hexagonal InN. The incorporation of nitrogen appears to suppress the growth of indium oxide, however crystallites of InN or In2O3 with sizes of a few dozen nanometers may exist within the film, which are not easily detected by XRD. Former studies on ZnON films also revealed that nanocrystallites could be observed by high resolution transmission electron microscopy (TEM)8. In this regard, further TEM analyses were performed on InON, which indicate that 4


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unlike ZnON8, no particular capping layers form upon annealing. Figures 2 (a) and (b) are cross-sectional TEM images of pristine and annealed (300 °C for 1 hour in air) InON, respectively. However, both InON layers appear to contain distinct clusters within the bulk, which crystallize after thermal treatment. The cluster in a magnified image of as deposited InON (figure 2 (c)) does not exhibit any crystallinity, whereas a nanocrystalline structure is manifested in the one in annealed InON (figure 2 (d)). Thorough examinations by electron energy loss spectroscopy (EELS) and nano-beam diffraction revealed that the matrix consists of amorphous InON, and the clusters are indium oxide (InOx). The optical transmittance was measured for In2O3, InON, and InN films as shown in figure 3 (a). The optical band gap values of each film were extracted using the Tauc method21, as shown in figure 3 (b). As the film becomes rich in nitrogen (In2O3 → InON → InN), the optical transmittance and optical band gap of the corresponding film decreases in the visible region (400-800 nm). The extracted optical band gap values of In2O3, InON, and InN are 2.54, 1.92 and 1.35 eV, respectively. In order to examine the chemical composition and bond properties of each film, Xray photoelectron spectroscopy (XPS) analyses were carried out. The relative atomic compositions of In2O3, InON, and InN layers obtained by XPS depth profiling are listed in table 2. The results indicate that the atomic ratio of In2O3 thin-film is close to perfect stoichiometry. Note that InN contains approximately 22 at. % of oxygen, which may occur by the oxidation of InN when exposed to air. Figures 4 (a) and (b) consist of the XPS O 1s peak spectra of In2O3 and InON films. The O 1s peak spectra were resolved into two sub-peaks labeled A and B, which are generally known to originate from oxygen forming metal-oxygen bonds and near oxygen vacant sites (VO), respectively22. Compared to In2O3, the fraction of the B sub-peak in InON is significantly smaller (26.9 → 6.7%). Generally, the VO levels are located deep in the forbidden band-gap, near the valence band maximum (VBM). When nitrogen is incorporated, the VBM is shifted upwards, by approximately the difference in optical band gap between In2O3 and InON (~0.62 eV). As a result, most VO states that influence the In2O3 properties are anticipated to become effectively passivated by the VBM being shifted up. Figures 4 (c) and (d) consist of the XPS N 1s peaks of InON and InN films. The N 1s peaks were resolved into three different sub-peaks C, D and E. The lowest energy sub-peak C originates from nitrogen forming metal-nitrogen bonds, and the middle sub-peak D arises 5



from oxynitride(ON) bonds23. The highest energy sub-peak E represents mostly NO2 bonds24. The InN film exhibits strong C and weak D sub-peaks. The oxygen content in InN appears to be manifested by the sub-peak D. The fraction of sub-peak D in InON is higher than that in InN, despite its relatively low nitrogen content. On the other hand, an additional sub-peak E is observed in the XPS spectrum obtained from the InON layer, which arises from the relatively high oxygen content. Figure 4 (e) shows the XPS In 3d peak intensities of each film, where no particular difference is observed. The transfer characteristics of the InON TFT are shown in figure 5 (a), where the inset shows a schematic diagram of the device structure. The optimized channel layer thickness is 7 nm, and the corresponding linear and saturation field-effect mobility values are 9.55 and 7.56 cm2/Vs, respectively. Figure 5 (b) shows the comparative transfer curves with different semiconductors and active layer thicknesses. The InN TFT exhibits a completely conductive behavior because of its high carrier concentration (table 1). The switching characteristics of the InON TFT with a 11 nm-thick active layer display a relatively negative threshold voltage (VTH) with elevated leakage current levels, whereas the application of a 7 nm-thick channel results in higher on/off ratio and saturation field-effect mobility. This is mainly due to the reduced number of excess carriers that make it more difficult for the gate voltage to modulate the channel current between the on and off states. The In2O3 TFTs exhibit inferior characteristics than InON devices, with low field effect mobility values that do not exceed 2 cm2/Vs. The representative transfer parameters of each device are listed in table 3. To evaluate the effect of nitrogen incorporation on the InON device stability, negative bias stress (NBS), positive bias stress (PBS) and negative bias illumination stress (NBIS) tests were conducted as shown in figures 6 (a)-(c). As the stress time increases, InON TFTs undergo negative (NBS, NBIS) and positive (PBS) shifts in threshold voltage (∆VTH) without significant degradation in the device performance. The ∆VTH values under NBS, PBS, and NBIS are -0.18, 0.59, and -1.51 V respectively. Figure 6 (d) shows the ∆VTH values under NBS, PBS, and NBIS of the In2O3 and InON TFTs as a function of stress time. The ∆VTH values after 1 hour of each stress are listed in table 4. The NBS and PBS results in the dark are similar for the In2O3 and InON TFTs, however the NBIS results differ largely. In the case of NBIS, photon radiation is expected to induce excess free carriers by either the ionization of the oxygen vacancies (VOs) or the formation of peroxides that induce PPC effects in oxide semiconductors, which is accompanied with large negative shifts in the 6


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threshold voltage25-27. As predicted, In2O3 devices undergo relatively large negative shifts in VTH (∆VTH = -8.91 V) while InON TFTs are more stable (∆VTH = -1.51 V). The passivation of VO states by nitrogen incorporation is suggested to have improved the NBIS stability of the InON. Figure 7 shows the sheet resistance change of ZnON, annealed ZnON (250 °C, 1 hour)8 and as-deposited InON films as a function of air exposure time (days). ZnON is fully converted into ZnO after 14 days. When ZnON is annealed, a thin capping layer forms on the surface and exhibits higher air stability. However here ZnON also converts into ZnO after 57 days. However, as-deposited InON maintains its sheet resistance even after 200 days. To understand this difference between ZnON and InON, DFT calculations were carried out to estimate the formation energies of Zn3N2 and InN by the following equations: 48 Zn + 16 N → 16 Zn3N2

(1)

36 In + 36 N → 36 InN

(2)

Here it is assumed that the N-rich ZnON films are mostly composed of Zn3N2, which convert to ZnO upon prolonged exposure to air. The calculated formation energies are 0.55 eV/atom for Zn3N2 and 0.22 eV/atom for InN. The formation energy of InN is much lower than that of Zn3N2, so the decomposition of In-N bonds is anticipated to be more sluggish. The high electron mobility and air stability of InON semiconductors thus make this material suitable for the fabrication of high performance TFTs with acceptable durability.

Conclusion In this work, the physical, chemical, and electrical properties of InON semiconductor were studied by experimental analyses and first principles calculations. In2O3, InON and InN films were grown by reactive RF sputtering using an In metal target, and the film properties were investigated along with TFT characteristics. XPS studies on the oxygen 1s peaks of In2O3 and InON thin films suggest that nitrogen anions effectively passivate the VO sites. This has an effect of improving the NBIS reliability of InON TFTs in comparison with In2O3 devices. Also, superior charge transport properties are observed in InON films and devices. Prolonged exposure to air show that as-deposited InON films are more durable than ZnON, 7



which readily convert to ZnO. DFT calculations suggest that the formation energy of InN is much lower than that of Zn3N2, so that the decomposition of In-N bonds does not occur spontaneously in air. InON semiconductors are thus good candidate materials for high performance TFTs, which not only exhibit high stability with respect to illumination, but also to moisture permeation from ambient air.

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (Jozeph Park) *E-mail: [email protected] (Hyun-Suk Kim) *E-mail: [email protected] (Yong Joo Kim) Notes The authors declare no competing financial interest

ACKNOWLEDGEMENTS This work was mainly supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant No: NRF-2013R1A4A1069528, NRF-2017M2B2A4049697) and partially by the MOTIE (Ministry of Trade, Industry & Energy (Grant No: 10051403)) and KDRC (Korea Display Research Corporation) support program for the development of future devices technology for display industry. And this work was also supported by the National Institute of Supercomputing and Network/Korea Institute of Science and Technology Information with supercomputing resources including technical support (Grant No: KSC-2017-C3-0005)

References (1) Nomura, K.; Otha, H.; Takagi, A.; Kamiya, T.; Hirano. M.; Hosono. H. Roomtemperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors. Nature (London). 2004, 432, 488–492. (2) Park, J. S.; Maeng, W.-J.; Kim, H.-S. & Park, J.-S. Review of recent developments in amorphous oxide semiconductor thin-film transistor devices. Thin Solid Films. 2012, 520, 1679–1693. (3) Park, J.-S.; Kim, H. & Kim, I.-D. Overview of electroceramic materials for oxide 8


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Page 9 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


semiconductor thin film transistors. J. Electroceramics. 2014, 32, 117–140. (4) Kamiya, T.; Nomura, K.; Hosono, H.; Present status of amorphous In-Ga-Zn-O thin-film transistors, Sci. Technol. Adv. Mater. 2010, 11 044305. (5) Yang, D.-G.; Kim, H.-D.; Kim, J. H.; Lee, S. W.; Park, J.; Kim, Y. J.; Kim, H.-S. The effect of sputter growth conditions on the charge transport and stability of In-Ga-Zn-O semiconductors, Thin Solid Films. 2017, 638, 361-366. (6) Kim, H.-S.; Jeon, S. H.; Park, J. S.; Kim, T. S.; Son, K. S.; Seon, J.-B.; Seo, S.-J.; Kim, S.-J.; Lee, E.; Chung, J. G.; Lee, H.; Han, S.; Ryu, M.; Lee, S. Y.; Kim, K. Anion control as a strategy to achieve high-mobility and high-stability oxide thin-film transistors, Sci. Rep. 2013, 3, 1459. (7) Ye, Y.; Lim, R.; White, J. M.; High mobility amorphous zinc oxynitride semiconductor material for thin film transistors, J. Appl. Phys. 2009, 106, 074512. (8) Park, J.; Kim, Y. S.; Ok, K.-C.; Park, Y. C.; Kim, H. Y.; Park, J.-S. & Kim, H.-S. A study on the electron transport properties of ZnON semiconductors with respect to the relative anion content. Sci. Rep. 2016, 6, 24787 (9) Park, J.; Kim, Y. S.; Kim, J. H.; Park, K.; Park, Y. C.; Kim, H.-S. The effects of active layer thickness and annealing conditions on the electrical performance of ZnON thin-film transistors. Journal of Alloys and Compounds. 2016, 688, 666-671 (10) Lee, E.; Kim, T.; Benayad, A.; Kim, H. G.; Jeon, S.; Park, G.-S. Ar plasma treated ZnON transistor for future thin film electronics. Appl. Phys. Lett. 2015, 107, 122105 (11) Sparvoli, M.; Onmori, R. K.; Jorge, F. O.; Gazziro, A. Indium oxynitride (InNO) radiation sensors calibration. IEEE Sens. J. 2017, 17, 2372-2376 (12) Amnuyswat, K.; Saributr, C.; Thanomngam, P.; Sungthong, A.; Porntheeraphat, S.; Sopitpan, S.; Nukeaw, J. XAFS analysis of indium oxynitride thin films grown on silicon substrates. X-Ray Spectrom. 2013, 42, 87-92 (13) Spavoli, M.; Mansano, R. D.; Chubaci, J. F. D. Study and Characterization of indium oxynitride photoconductors. Mat. Res. 2014, 17, 483-486 (14) J. P. Perdew.; K. Burke.; M. Ernzerhof. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865-3868 (15) Kresse, G.; Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. 1996, B. 54, 11169. (16) Blochl, P. E. Projector augmented-wave method. Phys. Rev. B. 1994, 50, 17953-17979. 9



(17) Sze, S. M.; Ng, K. K. Physics of Semiconductor Devices. Wiley, 2007. (18) Wu, J.; Walukiewicz, W. Band gaps of InN and group III nitride alloys. Superlatt. Microstruct. 2004, 34, 63-75 (19) Rinke, P.; Scheffler, M. Band gap and band parameters of InN and GaN form quasiparticle energy calculations based on exact-exchange density functional theory. Appl. Phys. Lett. 2006, 89, 161919 (20) Sparvoli, M.; Mansano, R. D.; Chubaci, J. F. D. Study of indium nitride and indium oxynitride band gaps. Mat. Res. 2013, 16, 850-852 (21) Tauc, J., Grihorovici, R. & Vancu, A. Optical properties and electronic structure of amorphous germanium. Phys. Status Solidi, 1966, B 15, 627–637. (22) An, Y.; Wang, S.; Duan, L.; Liu, J.; Wu, Z. Local Mn structure and room temperature ferromagnetism in Mn-doped In2O3 films. Appl. Phys. Lett. 2013, 102, 212411. (23) Himmerlich, M.; Koufaki, M.; Ecke, G.; Mauder, C.; Cimalla, V.; Schaefer, J. A.; Kondilis, A.; Pelekanos, N. T.; Modreanu, M.; Krischok, S.; Aperathitis, E. Effect of Annealing on the properties of indium-tin-oxynitride films as ohmic contacts for GaN-based optoelectronic devices. ACS Appl. Mater. Interfaces. 2009, 1, 1451-1456 (24) Shinoda, H.; Mutsukura N. Deposition of an InN thin film by a r.f. plasma-assisted reactive ion-beam sputtering deposition (R-IBSD) technique. Diam. Relat. Mat. 2002, 11, 896-900 (25) Lee, K. H.; Jung, J. S.; Son, K. S.; Park, J. S.; Kim, T. S.; Choi, R.; Jeong, J. K.; Kwon, J. Y.; Koo, B.; Lee, S. The effect of moisture on the photon-enhanced negative bias thermal instability in Ga-In-Zn-O thin film transistors, Appl. Phys. Lett. 2009, 95, 232106. (26) Shin, J. H.; Lee, J. S.; Hwang, C. S.; Park, S. H. K.; Cheong, W. S.; Ryu, M.; Byun, C.W.; Lee, J. I.; Chu, H. Y. Light effects on the bias stability of transparent ZnO thin film transistors, ETRI J. 2009, 31, 62-64. (27) Jeon, J.H.; Kim, J. H.; Ryu, M. K. Instability of an amorphous indium gallium zinc oxide TFT under bias and light illumination, J. Korean Phys. Soc. 2011, 58, 158-162.

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Figure Captions Figure 1. Grazing incidence angle X-ray diffraction (GIAXRD) patterns of In2O3, InON and InN films.

Figure 2. TEM cross-section images of (a) as deposited and (b) annealed InON. TEM images showing InOx cluster in (c) as deposited and (d) annealed InON. Figure 3. (a) Optical transmittance of In2O3, InON, and InN layers measured with a UV-Vis spectrophotometer. (b) Optical band gap values of In2O3, InON, and InN extracted using the Tauc plot method.

Figure 4. XPS O 1s spectra of (a) In2O3 and (b) InON. XPS N 1s spectra of (c) InON and (d) InN. (e) XPS In 3d spectra of In2O3, InON, and InN. Figure 5. (a) Schematic diagram of InON TFT (inset) and transfer characteristics at VD = 0.1 and 10 V. (b) Comparative transfer characteristics of In2O3, InON, and InN TFTs. Figure 6. Time evolution of the transfer characteristics under NBS, PBS and NBIS tests. (a) NBS, (b) PBS, and (c) NBIS of InON TFTs. (d) ∆VTH values under NBS, PBS and NBIS for In2O3 and InON TFTs, as a function of stress time.

Figure 7. Change in sheet resistance of ZnON, annealed ZnON, InON thin-films as a function of air exposure time.

11



Table Captions Table 1. Hall mobility, carrier concentration and sheet resistance of In2O3, InON, and InN thin films.

Table 2. Relative chemical composition of each element in the In2O3, InON, and InN layers, obtained by XPS depth profile analyses.

Table 3. Representative transfer parameters of the In2O3, InON, and InN TFTs. Table 4. ∆VTH values of each stress conditions of the In2O3 and InON TFTs.

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Table 1. Sheet resistance

Hall mobility

Carrier concentration

(㏀/sq)

(㎠/Vs)

(/㎤)

In2O3

N/A

N/A

N/A

InN

0.5

11.0

-6.11 x 1020

InON

3.2

32.3

-4.26 x 1019

Table 2. In (at%)

O (at%)

N (at%)

In2O3

41.54

58.46

0

InON

42.89

48.86

8.25

InN

51.35

22.82

25.83

Table 3. µFE

S.S

(㎠/Vs)

(V/dec)

InN TFT

N/A

InON TFT In2O3 TFT

VTH (V)

Ion/Ioff

N/A

N/A

N/A

7.56

0.39

-1.95

9.69 x 107

1.77

0.30

1.15

3.87 x 107

Table 4. NBS

PBS

NBIS

In2O3 TFT

-0.43 V

0.69 V

-8.91 V

InON TFT

-0.18 V

0.59 V

-1.51 V

13



InN (002)

Normalized Intensity (a. u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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InN (103) InN

InON In2O3 (222) In2O3 (400) In2O3

20

30

40

50

60 o

2 theta ( )

Figure 1.

14


70

80

Page 15 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2.

15



(a)

100 In2O3 80

InON

60

InN

3

2

2

(αhυ) (X10 eV /cm )

2

2

10

40

20

1

0 0.00

0.75

1.50

2.25

3.00

Photon Energy (eV)

300

400

500

600

700

800

Wavelength (nm)

(b) Optical band gap (eV)

Transmittance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 21

3.0

2.54

2.5

1.92

2.0

1.35

1.5 1.0 0.5 0.0

In2O3

InON

Figure 3. 16


InN

900

Page 17 of 21

(b)

Normalized Intensity (a.u.)

(a) O1s Peak

In2O3 Raw Fit O1: M-O Bond O2: Vo Bond

O1s Peak

InON Raw Fit O1: M-O Bond O2: Vo Bond

73.1 %

93.3 %

26.9 % 6.7 % 540

538

536

534

532

530

528

540

538

536

Binding Energy (eV)

534

532

530

528

Binding Energy (eV)

(c)

(d) N1s Peak

InN Raw Fit N1: In-N Bond N2: ON Bond

N1s Peak

InON Raw Fit N1: In-N Bond N2: ON Bond N3: NO2 Bond

89.4 %

16.8 %

69.8 %

13.4 %

10.6 %

408

405

402

399

396

393

408

405

Binding Energy (eV)

402

399

396

Binding Energy (eV)

(e) Normalized Intensity (a.u.)

Normalized Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In3d Peak In2O3 InON InN

450

440

Binding Energy (eV)

Figure 4.

17


393


Figure 5.

18


Page 18 of 21

Page 19 of 21

(a)

(b)

-3

10

-4

10

Drain Current (A)

-3

10

NBS

-5

10

-5

-6

10

-7

10

-8

10

-6

10

-7

10

-8

10

0s 600 s 1200 s 1800 s 2400 s 3000 s 3600 s

-9

10

-10

10

-11

10

-30

(c) 10

-3

-4

10

0s 600 s 1200 s 1800 s 2400 s 3000 s 3600 s

-9

10

-10

10

-11

10

-12

10

PBS

-4

10

10

-12

-20

-10

0

10

20

30

Gate Voltage (V)

10

(d)

-30

-20

-10

0

10

20

30

Gate Voltage (V) 5

NBIS

-5

10

-6

0

10

-7

10

∆VTH (V)

Drain Current (A)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


-8

10

0s 600 s 1200 s 1800 s 2400 s 3000 s 3600 s

-9

10

-10

10

-11

10

In2O3 NBS In2O3 PBS In2O3 NBIS InON NBS InON PBS InON NBIS

-12

10

-30

-20

-10

0

10

20

-5

-10

30

0

Gate Voltage (V)

600

1200 1800 2400 3000 3600

Stress time (s)

Figure 6.

19



20

Sheet resistance (kΩ/sq)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 21

Range over th @ 14 days

Range over th @ 57 days

ZnON

annealed ZnON

16

12

8

InON

4

0

0

10 20 30 40 50 60

190

Time (day)

Figure 7.

20


200

Page 21 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table of Contents (TOC)

21


Highly Stable Thin-Film Transistors based on Indium Oxynitride

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