Effects of the thickness of the channel layer on the device performance of InGaZnO thin-film-transistors

Woo, Chang Ho; Kim, Y.Y.; Kong, Bo Hyun; Cho, Hyung Koun

doi:10.1016/j.surfcoat.2010.07.036

Cited by 20 publications

(5 citation statements)

References 14 publications

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“…in the 100-nm thick IGZO TFT, respectively. The degraded SS value and the shifted V on in the negative V GS direction can be commonly interpreted as consequences of the total defect states and free carrier numbers being increased as the T IGZO values increased, which is consistent with previous publications [ 23 , 24 ] and in agreement with the C – V measurements in Figure 3 . Generally, the SS value is an indicator of the maximum area density of state ( N t ), including the interfacial ( D it ) and the semiconductor bulk traps ( N bulk ).…”

Section: Resultssupporting

confidence: 92%

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

Wang

Zhao

et al. 2018

Materials

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In this study, the initial electrical properties, positive gate bias stress (PBS), and drain current stress (DCS)-induced instabilities of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with various active layer thicknesses (TIGZO) are investigated. As the TIGZO increased, the turn-on voltage (Von) decreased, while the subthreshold swing slightly increased. Furthermore, the mobility of over 13 cm2·V−1·s−1 and the negligible hysteresis of ~0.5 V are obtained in all of the a-IGZO TFTs, regardless of the TIGZO. The PBS results exhibit that the Von shift is aggravated as the TIGZO decreases. In addition, the DCS-induced instability in the a-IGZO TFTs with various TIGZO values is revealed using current–voltage and capacitance–voltage (C–V) measurements. An anomalous hump phenomenon is only observed in the off state of the gate-to-source (Cgs) curve for all of the a-IGZO TFTs. This is due to the impact ionization that occurs near the drain side of the channel and the generated holes that flow towards the source side along the back-channel interface under the lateral electric field, which cause a lowered potential barrier near the source side. As the TIGZO value increased, the hump in the off state of the Cgs curve was gradually weakened.

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Section: Resultssupporting

confidence: 92%

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

Wang

Zhao

et al. 2018

Materials

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“…The slightly degraded SS value and negatively shifted V T of both the Al-MIA and Al-PL IGZO TFTs, as the Al coverage increases, can be rationalized by the increased carrier density. [48,54,55] Furthermore, since the SS change correlates with the total trap density (N T ) within the device channel region according to the equation ΔSS = qkTN T t ch ln(10)/C ox , [56] where q is the electron charge, k is Boltzmann's constant, T is the temperature, and t ch is the channel thickness, the N T of these devices can be extracted. It is found that N T of the Al-MIA TFTs (2.71 × 10 16 eV −1 cm −3 ) is far lower than that of the Al-PL TFTs (3.64 × 10 17 eV −1 cm −3 ).…”

Section: Resultsmentioning

confidence: 99%

Readily Accessible Metallic Micro‐Island Arrays for High‐Performance Metal Oxide Thin‐Film Transistors

et al. 2022

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versus conventional amorphous silicon TFTs, as well as large area processability at low temperatures. [13][14][15][16] Furthermore, MOTFTs are less affected by short channel effects. [17][18][19] As in other transistor technologies, MOTFT performance strongly depends on the intrinsic semiconductor channel properties as well as the channel interfacial characteristics, including that of the top surface. [20][21][22] Furthermore, MOTFTs are limited by uncontrollable back channel trap densities, restricting their application in high-resolution displays, as well as 3D and virtual reality devices. [7,[23][24][25][26][27] Recently, several strategies were reported to enhance the performance of MOTFTs by adopting new device architectures, including dual gate implantation, [28][29][30] high-k insulators, [31][32][33] and semiconducting heterostructures. [34][35][36][37][38] Among these strategies, low-dimensional bi-or multilayer heterostructures of different MOs have enhanced the carrier mobility and drive current in MOTFTs. [39,40] These improvements typically originate from confined free electrons within the potential well of the heterointerface between two semiconductors having large Fermi energy differences. [41] However, although these approaches are noteworthy, limitations in available component materials and control of leakage currents have compromised the fidelity of this platform. [37,38] Another approach to enhance performance Thin-film transistors using metal oxide semiconductors are essential in many unconventional electronic devices. Nevertheless, further advances will be necessary to broaden their technological appeal. Here, a new strategy is reported to achieve high-performance solution-processed metal oxide thin-film transistors (MOTFTs) by introducing a metallic micro-island array (M-MIA) on top of the MO back channel, where the MO is a-IGZO (amorphous indium-gallium-zinc-oxide). Here Al-MIAs are fabricated using honeycomb cinnamate cellulose films, created by a scalable breath-figure method, as a shadow mask. For IGZO TFTs, the electron mobility (µ e ) increases from ≈3.6 cm 2 V −1 s −1 to near 15.6 cm 2 V −1 s −1 for optimal Al-MIA dimension/ coverage of 1.25 µm/51%. The Al-MIA IGZO TFT performance is superior to that of controls using compact/planar Al layers (Al-PL TFTs) and Au-MIAs with the same channel coverage. Kelvin probe force microscopy and technology computer-aided design simulations reveal that charge transfer occurs between the Al and the IGZO channel which is optimized for specific Al-MIA dimensions/surface channel coverages. Furthermore, such Al-MIA IGZO TFTs with a high-k fluoride-doped alumina dielectric exhibit a maximum µ e of >50.2 cm 2 V −1 s −1 . This is the first demonstration of a micro-structured MO semiconductor heterojunction with submicrometer resolution metallic arrays for enhanced transistor performance and broad applicability to other devices.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202205871.

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“…The increase in the electron concentration enhances the formation of the percolation conduction path in IGTO and makes it difficult to turn off the TFT [30][31][32]. In addition, a higher carrier concentration within the channel increases the SS value of the TFT [33,34]. Therefore, a lower value of V TH and higher values of µ FE and SS in the 5 and 8 nm thick Al-capped IGTO TFTs than in the uncapped and 3 nm thick Al-capped IGTO TFTs can be attributed to the larger concentration of V O within the IGTO channel layer caused by the stronger oxidation power of the thicker Al capping layer.…”

Section: Resultsmentioning

confidence: 99%

Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness

et al. 2020

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We examined the effects of aluminum (Al) capping layer thickness on the electrical performance and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). The Al capping layers with thicknesses (tAls) of 3, 5, and 8 nm were deposited, respectively, on top of the IGTO thin film by electron beam evaporation, and the IGTO TFTs without and with Al capping layers were subjected to thermal annealing at 200 °C for 1 h in ambient air. Among the IGTO TFTs without and with Al capping layers, the TFT with a 3 nm thick Al capping layer exhibited excellent electrical performance (field-effect mobility: 26.4 cm2/V s, subthreshold swing: 0.20 V/dec, and threshold voltage: −1.7 V) and higher electrical stability under positive and negative bias illumination stresses than other TFTs. To elucidate the physical mechanism responsible for the observed phenomenon, we compared the O1s spectra of the IGTO thin films without and with Al capping layers using X-ray photoelectron spectroscopy analyses. From the characterization results, it was observed that the weakly bonded oxygen-related components decreased from 25.0 to 10.0%, whereas the oxygen-deficient portion was maintained at 24.4% after the formation of the 3 nm thick Al capping layer. In contrast, a significant increase in the oxygen-deficient portion was observed after the formation of the Al capping layers having tAl values greater than 3 nm. These results imply that the thicker Al capping layer has a stronger gathering power for the oxygen species, and that 3 nm is the optimum thickness of the Al capping layer, which can selectively remove the weakly bonded oxygen species acting as subgap tail states within the IGTO. The results of this study thus demonstrate that the formation of an Al capping layer with the optimal thickness is a practical and useful method to enhance the electrical performance and stability of high-mobility IGTO TFTs.

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Effects of the thickness of the channel layer on the device performance of InGaZnO thin-film-transistors

Cited by 20 publications

References 14 publications

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

Drain Current Stress-Induced Instability in Amorphous InGaZnO Thin-Film Transistors with Different Active Layer Thicknesses

Readily Accessible Metallic Micro‐Island Arrays for High‐Performance Metal Oxide Thin‐Film Transistors

Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness

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