The full form of TFT is thin-film transistors.
These are transistors that are relatively thin in comparison to the lane of the device. Here the transistors are grown on a non-conducting substrate. This is in contrast to the traditional transistors as in those the semiconductor material is generally integrated into the substrate. The thin films of active semiconductors are stacked on top of each other with a dielectric layer to create such a transistor. The major use of TFT is found in LCD monitors. They consume less amount of energy and provide much clearer details. That being said it is also costlier than simple monochrome displays and causes some problems based on the viewing angle.
Transistors: These are semiconductor devices that are used to amplify or switch electrical signals and power. The idea of a transistor was proposed by Julius Edgar and it was created by John Bardeen and Walter Brattain in the year1947. They are used in all modern electrical appliances. Ranging from its use in computers and other electronics, metal–oxide–semiconductor field-effect transistors also known as MOSFET is one of the most important semiconductors to have ever been made. Its properties can be listed as follows:
- It can be used for gain which is applying a small signal between two terminals to control communication between larger terminals.
- It can be used as an amplifier to amplify the amount of current or voltage.
- It can also be used as a switch to control the flow of current in a circuit.
Types of Transistors:
We must understand the different types of transistors before studying specifically about thin-film transistors. They are:
- Tunnel Field-Effect transistor: This type of transistor is mainly used for experiments. Similar in structure to MOSFET it differs in switching mechanisms hence making it useful in low power electronics.
- Bipolar junction transistor: Here both electrons and holes are used as carriers. Holes are generally spaces devoid of a terminal electron consisting of a positive charge. They can be of two types N-type and P-type transistors. They are used to make high-speed digital logic, amplifiers, temperature sensors, etc. The different types of BJT transistors can be listed below:
- Heterojunction bipolar transistor
- Darlington transistors
- Field-Effect transistor: It makes the use of an electrical field to control the flow of current in a semiconductor. Generally consisting of three terminals- source, gate, drain it is responsible for controlling the current by varying the amount of voltage allowed to the gate, which changes the conductivity from the source to the drain. AN advantage of FET over a BJT is that it produces less noise and is generally found in low noise instruments. The most common use of a field-effect transistor is found in amplifiers. The different types of FET are:
- Metal–oxide–semiconductor field-effect transistor
- Thin- Film transistor.
- Power Mosfet
- Carbon nanotube field-effect transistor
Manufacture: A range of semiconducting materials can be used for the construction of Thin Film Transistors. Historically the most widely used material was amorphous silicon as it was the most widely available as well. This being said there were some challenges with it being very low in mobility and also having large variability between devices. Thus other materials such as cadmium selenide, indium gallium zinc oxide, carbon nanotubes, etc have also been used in thin-film transistors. For the deposition of the semiconductor, various specialised techniques such as chemical vapour deposition, atomic layer deposition, and sputtering are used. Also, solution-based techniques such as printing or spray coating are used.
Applications: The field of transistors has evolved a lot in the recent century and has helped us in building stronger and better performing devices. TFT is another such revolution in the field of digital imaging and screening. The best use of thin-film transistors can be found in liquid crystal display technology. They are responsible for improving the image quality. They also find applications in general radiography. AMOLED displays are generally made up of TFTs. Every pixel is made up of different transistors hence they can be individually regulated quickly and give crystal clear images.
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