Field-Effect Device Using Quasi-Two-Dimensional Electron Gas in Mass-Producible Atomic-Layer-Deposited Al2O3/TiO2 Ultrathin (&lt;10 nm) Film Heterostructures

deposition (PLD), and radiofrequency sputtering. [2,[11][12][13] Nevertheless, solutionprocessing of MO precursors holds significant promise for lower cost production and compatibility with flexible substrates. [2,9,14,15] In this regard, indium oxide (In 2 O 3 ) is one of the most investigated solution-processed oxide semiconductors, [7,[16][17][18][19][20][21] however, the carrier density of pristine In 2 O 3 is difficult to control and In 2 O 3 films are usually polycrystalline, limiting their performance uniformity over large areas as well as mechanical flexibility. [22] To address both of these issues, metals such as Zn and/or Ga are added to In 2 O 3 , enabling the growth of amorphous MO thin films with enhanced electronic properties and ultimately affording far more stable TFT characteristics. [22][23][24][25][26] Recently, we reported a new strategy for high performance, near-zero threshold voltage (V Th ), bias stress-stable, and amorphous In 2 O 3 films and TFTs by simply doping the In 2 O 3 with an electrically insulating polymer such as poly(4-vinylphenol) (PVP) or polyethylenimine (PEI) to afford amorphous MO:polymer blend semiconducting nanocomposites. [2,17,22] The attraction of electron-rich PEI versus PVP is that the TFT High-performance solution-processed metal oxide (MO) thin-film transistors (TFTs) are realized by fabricating a homojunction of indium oxide (In 2 O 3 ) and polyethylenimine (PEI)-doped In 2 O 3 (In 2 O 3 :x% PEI, x = 0.5-4.0 wt%) as the channel layer. A two-dimensional electron gas (2DEG) is thereby achieved by creating a band offset between the In 2 O 3 and PEI-In 2 O 3 via work function tuning of the In 2 O 3 :x% PEI, from 4.00 to 3.62 eV as the PEI content is increased from 0.0 (pristine In 2 O 3 ) to 4.0 wt%, respectively. The resulting devices achieve electron mobilities greater than 10 cm 2 V −1 s −1 on a 300 nm SiO 2 gate dielectric. Importantly, these metrics exceed those of the devices composed of the pristine In 2 O 3 materials, which achieve a maximum mobility of ≈4 cm 2 V −1 s −1 . Furthermore, a mobility as high as 30 cm 2 V −1 s −1 is achieved on a high-k ZrO 2 dielectric in the homojunction devices. This is the first demonstration of 2DEG-based homojunction oxide TFTs via band offset achieved by simple polymer doping of the same MO material. Thin-Film TransistorsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.As a consequence of their outstanding charge transport properties and excellent optical transparency, metal oxide thin-film transistors (MOTFTs) have been heavily investigated for applications in state-of-the-art flat panel display technologies and next-generation electronics. [1][2][3][4][5][6][7][8][9][10] To date, several growth techniques have been utilized to fabricate MO films for TFTs including atomic layer deposition (ALD), pulsed-laser

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“…Application of a V GS < 0 V can shut down the channel by an identical mechanism. A similar phenomenon has been reported for other 2DEG TFTs …”

Section: Performance Metrics Of the Indicated Tft Devices On Si/sio2 supporting

confidence: 89%

Polymer Doping Enables a Two‐Dimensional Electron Gas for High‐Performance Homojunction Oxide Thin‐Film Transistors

et al. 2018

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“…An amorphous Al 2 O 3 film, with a thickness of ≈3 nm, was grown on the crystalline TiO 2 (≈10 nm) layer. This TiO 2 layer was a polycrystalline anatase phase, as reported by our group . The interface between the Al 2 O 3 and TiO 2 layers was sharp, which implies that the layers did not intermix.…”

Section: Resultssupporting

confidence: 73%

“…Unfortunately, the electron density could not be tailored for the given fabrication method, in which electrons originated from the polar catastrophe mechanism based on the epitaxial interface . For the Al 2 O 3 /TiO 2 heterostructure, it has been reported that oxygen vacancies were generated on the surface of the TiO 2 layer during the Al 2 O 3 ALD process . By the action of trimethylaluminum (TMA), which is an Al‐precursor in the Al 2 O 3 ALD process, Ti 4+ in the fully oxidized TiO 2 layer reduces to Ti 3+ on the surface of the TiO 2 layer, which causes the generation of oxygen vacancies on the TiO 2 surface, as reported in ref.…”

Section: Resultsmentioning

confidence: 99%

“…By the action of trimethylaluminum (TMA), which is an Al‐precursor in the Al 2 O 3 ALD process, Ti 4+ in the fully oxidized TiO 2 layer reduces to Ti 3+ on the surface of the TiO 2 layer, which causes the generation of oxygen vacancies on the TiO 2 surface, as reported in ref. . The oxygen vacancies donate electrons to the Ti 3d orbit due to its low activation energy (0.01–0.05 eV), thus, the oxygen vacancy number changes the electron density at the interface of the Al 2 O 3 /TiO 2 heterostructure .…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, the growth temperature of the LAO layer can reach 750 °C, which limits wide application of the gas sensors . The creation of 2DEG using atomic layer deposition (ALD) technique has been reported by our group, recently …”

Section: Introductionmentioning

confidence: 99%

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High‐Performance, Transparent Thin Film Hydrogen Gas Sensor Using 2D Electron Gas at Interface of Oxide Thin Film Heterostructure Grown by Atomic Layer Deposition

Kim

Jung

et al. 2018

Adv Funct Materials

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A high-performance, transparent, and extremely thin (<15 nm) hydrogen (H 2 ) gas sensor is developed using 2D electron gas (2DEG) at the interface of an Al 2 O 3 /TiO 2 thin film heterostructure grown by atomic layer deposition (ALD), without using an epitaxial layer or a single crystalline substrate. Palladium nanoparticles (≈2 nm in thickness) are used on the surface of the Al 2 O 3 /TiO 2 thin film heterostructure to detect H 2 . This extremely thin gas sensor can be fabricated on general substrates such as a quartz, enabling its practical application. Interestingly, the electron density of the Al 2 O 3 /TiO 2 thin film heterostructure can be tailored using ALD process temperature in contrast to 2DEG at the epitaxial interfaces of the oxide heterostructures such as LaAlO 3 / SrTiO 3 . This tunability provides the optimal electron density for H 2 detection. The Pd/Al 2 O 3 /TiO 2 sensor detects H 2 gas quickly with a short response time of <30 s at 300 K which outperforms conventional H 2 gas sensors, indicating that heating modules are not required for the rapid detection of H 2 . A wide bandgap (>3.2 eV) with the extremely thin film thickness allows for a transparent sensor (transmittance of 83% in the visible spectrum) and this fabrication scheme enables the development of flexible gas sensors.

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Recent Progress on Amorphous Oxide Semiconductor Thin‐Film Transistors Using the Atomic Layer Deposition Technique

Jeong

Park

2022

Amorphous Oxide Semiconductors

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Field-Effect Device Using Quasi-Two-Dimensional Electron Gas in Mass-Producible Atomic-Layer-Deposited Al₂O₃/TiO₂ Ultrathin (<10 nm) Film Heterostructures

Cited by 52 publications

References 29 publications

Polymer Doping Enables a Two‐Dimensional Electron Gas for High‐Performance Homojunction Oxide Thin‐Film Transistors

Polymer Doping Enables a Two‐Dimensional Electron Gas for High‐Performance Homojunction Oxide Thin‐Film Transistors

High‐Performance, Transparent Thin Film Hydrogen Gas Sensor Using 2D Electron Gas at Interface of Oxide Thin Film Heterostructure Grown by Atomic Layer Deposition

Recent Progress on Amorphous Oxide Semiconductor Thin‐Film Transistors Using the Atomic Layer Deposition Technique

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