Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

https://iopscience.iop.org/article/10.1088/1468-6996/11/4/044305/pdf

Present status of amorphous In–Ga–Zn–O thin-film transistors

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

A low-temperature, solution-based preparation of amorphous, metal oxide semiconducting thin-films is reported. This ‘sol–gel on chip’ hydrolysis approach yields thin-film transistors with high field-effect mobilities, reproducible and stable turn-on voltages and high operational stability.

Low-temperature, high-performance solution-processed metal oxide thin-film transistors formed by a ‘sol–gel on chip’ process

Here we summarize recent progress in the development of electrolyte-gated transistors (EGTs) for organic and printed electronics. EGTs employ a high capacitance electrolyte as the gate insulator; the high capacitance increases drive current, lowers operating voltages, and enables new transistor architectures. Although the use of electrolytes in electronics is an old concept going back to the early days of the silicon transistor, new printable, fast-response polymer electrolytes are expanding the potential applications of EGTs in flexible, printed digital circuits, rollable displays, and conformal bioelectronic sensors. This report introduces the structure and operation mechanisms of EGTs and reviews key developments in electrolyte materials for use in printed electronics. The bulk of the article is devoted to electrical characterization of EGTs and emerging applications.

Electrolyte-gated transistors for organic and printed electronics

We reported on a two-dimensional simulation of electrical properties of the radio frequency (rf) sputter amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFT used in this work has the following performance: field-effect mobility (μeff) of ∼12 cm2/V s, threshold voltage (Vth) of ∼1.15 V, subthreshold swing (S) of ∼0.13 V/dec, and on/off ratio over 1010. To accurately simulate the measured transistor electrical properties, the density-of-states model is developed. The donorlike states are also proposed to be associated with the oxygen vacancy in a-IGZO. The experimental and calculated results show that the rf sputter a-IGZO TFT has a very sharp conduction band-tail slope distribution (Ea=13 meV) and Ti ohmic-like source/drain contacts with a specific contact resistance lower than 2.7×10−3 Ω cm2.

Two-dimensional numerical simulation of radio frequency sputter amorphous In–Ga–Zn–O thin-film transistors

We studied both the wavelength and intensity dependent photo‐responses (photofield‐effect) in amorphous In‐Ga‐Zn‐O (a‐IGZO) thin‐film transistors (TFTs). During the a‐IGZO TFT illumination with the wavelength range from 460∼660 nm (visible range), the off‐state drain current (IDS_off) only slightly increased while a large increase was observed for the wavelength below 400 nm. The observed results are consistent with the optical gap of ∼3.05eV extracted from the absorption measurement. The a‐IGZO TFT properties under monochromatic illumination (λ=420nm) with different intensity was also investigated and IDS_off was found to increase with the light intensity. Throughout the study, the field‐effect mobility (μeff) is almost unchanged. But due to photo‐generated charge trapping, a negative threshold voltage (Vth) shift is observed. The mathematical analysis of the photofield‐effect suggests that a highly efficient UV photocurrent conversion process in TFT off‐region takes place. Finally, a‐IGZO mid‐g...

https://www.tandfonline.com/doi/pdf/10.1080/15980316.2008.9652066

Photofield‐effect in amorphous In‐Ga‐Zn‐O (a‐IGZO) thin‐film transistors

https://ir.nctu.edu.tw:443/bitstream/11536/11696/1/000241956800025.pdf

Low-voltage organic thin-film transistors with polymeric nanocomposite dielectrics

We studied the optical and electrical properties of the amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs). To develop a-IGZO density-of-states model, intrinsic a-IGZO optical properties such as optical band gap and Urbach energy, and TFT characteristics under illumination are investigated. During the a-IGZO TFTs illumination with the wavelengths ranging from 460 to 660 nm, the off-state drain current only slightly increases while a large increase was observed for the wavelength below 400 nm. Threshold voltage and subthreshold swing are also only slightly modified between 460 to 660 nm, while field-effect mobility is almost unchanged in the investigated photon energy range. The observed results are consistent with the a-IGZO optical energy band gap of about 3.05 eV. This study suggest that the a-IGZO TFTs are light sensitive above 3.0 eV and photogenerated electrons are more mobile than holes within device channel region.

/pdf/p-13-photosensitivity-of-amorphous-igzo-tfts-for-active-1mf2fq0cn0.pdf

P‐13: Photosensitivity of Amorphous IGZO TFTs for Active‐Matrix Flat‐Panel Displays

Embodiments of the present invention are directed to a termination structure provided for a trench DMOS device to reduce occurrence of current leakage resulting from electric field crowding at the border of the active area and a method of manufacturing the same. In one embodiment, the termination structure for the trench DMOS device comprises a substrate of a first type conductivity and an epitaxial layer of the first type conductivity over the substrate. The epitaxial layer has a lower doping concentration than the substrate. A body region of a second type conductivity is provided within the epitaxial layer. A trench extends through the body region between an active area and an edge of the substrate. A gate oxide layer lines the trench and extends to the upper surface of the body region between the trench and the active area. A passivation layer is formed on the gate oxide layer, including sidewalls and a bottom surface of the trench. A metal layer covers portions of the passivation layer on the side walls of the trench to expose a part of the passivation layer over the bottom surface of the trench.

Chiao-Shun Chuang

Papers

Two-dimensional numerical simulation of radio frequency sputter amorphous In–Ga–Zn–O thin-film transistors

Photofield‐effect in amorphous In‐Ga‐Zn‐O (a‐IGZO) thin‐film transistors

Low-voltage organic thin-film transistors with polymeric nanocomposite dielectrics

P‐13: Photosensitivity of Amorphous IGZO TFTs for Active‐Matrix Flat‐Panel Displays

Termination structure for trench DMOS device and method of making the same