science

Oxide thin-film transistor

Oxide thin-film transistor is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Oxide thin-film transistor rather than just read about it. In short: An oxide thin-film transistor (oxide TFT) or metal oxide thin film transistor is a type of thin film transistor where the semiconductor is a metal oxide compound. An oxide TFT is distinct from a metal oxide field effect transistor (MOSFET) where the word "oxide" refers to the insulating gate dielectric (normally silicon dioxide).

Key takeaways

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Reference excerpt

An oxide thin-film transistor (oxide TFT) or metal oxide thin film transistor is a type of thin film transistor where the semiconductor is a metal oxide compound. An oxide TFT is distinct from a metal oxide field effect transistor (MOSFET) where the word "oxide" refers to the insulating gate dielectric (normally silicon dioxide). In an oxide TFT, the word oxide refers to the semiconductor. Oxide TFTs have applications as amplifiers to deliver current to emitters in display backplanes.

History The first transistor employing a metal oxide as the semiconductor was reported in 1964 by Klasens and Koelmans at Philips Research Laboratories. However, oxide TFTs were seldom considered again for several decades after this. It wasn't until the early 2000's that Hideo Hosono, who was studying transparent conducting oxides, discovered that oxysulfides and indium gallium zinc oxide could be used as semiconductors in TFTs. Soon after, John Wager at Oregon State University reported oxide TFTs employing the binary oxide zinc oxide as the semiconductor.

Properties Oxides have several properties which make them desirable over hydrogenated amorphous silicon (a-Si:H), which was the incumbent TFT technology in the early 2000's. Firstly, the electron mobility is roughly 100 times higher in oxide TFTs. Because the source-drain current in transistors is linearly proportional to electron mobility, so too are the amplification properties. The result of this is that smaller transistors can be used to provide the same current. In a display this means that a higher resolution and switching speed is possible. a-Si:H additionally suffers from issues with environmental stability, such as the Staebler-Wronski Effect. As oxides are already oxidized, they are generally more environmentally stable, however they do experience a phenomenon called Negative Bias Illumination Stress (NBIS) where the threshold voltage changes under constant illumination. Most n-type (electron transporting) oxide TFTs employ semiconductors that have a wide bandgap; generally greater than 3 eV. For this reason they are attractive for use in fully transparent electronics. Their wide bandgap also means they have a low off-current, and hence a high on/off ratio; a desirable property for well-defined on- and off-states. One significant drawback with oxide TFTs is that there are very few p-type (hole transporting) metal oxide semiconductors. While not a significant problem when providing amplification to emitters, this does mean oxide semiconductors are less suitable for complementary logic, and hence information processing.

Growth Metal oxide semiconductors are typically deposited using sputtering, a vacuum-based growth technique resulting in an amorphous or polycrystalline layer. Oxides can also be deposited from solution, such as via spin-coating or spray coating.

Commercial use Several companies have adopted oxide TFTs as a platform for display drivers. Notably Sharp in 2012, and Apple in 2013.

References

Illustrations

Worked examples

Example 1 — a first encounter with Oxide thin-film transistor

Start with the simplest possible case. Write down what Oxide thin-film transistor claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Oxide thin-film transistor before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Oxide thin-film transistor ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Oxide thin-film transistor

In research: Oxide thin-film transistor appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Oxide thin-film transistor in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Oxide thin-film transistor is common in secondary-school and first-year university syllabi. It links to neighbouring topics Semiconductor devices, Transistor types, so understanding it makes those chapters shorter.
In everyday life: Look for Oxide thin-film transistor outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Oxide thin-film transistor in 20 minutes

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Frequently asked questions

What is Oxide thin-film transistor in simple terms?

Why does Oxide thin-film transistor matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Oxide thin-film transistor?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Oxide thin-film transistor.