A transistor is a semiconductor device used in electronics for amplification, switching, and modulation. It comes in two main types: bipolar junction transistors (BJTs) and field-effect transistors (FETs).
Transistors, in a broad sense, refer to single components based on semiconductor materials. They possess various functions such as detection, rectification, amplification, switching, voltage regulation, and signal modulation. Transistors can be used for a wide range of digital and analog applications.
Transistors refer to all single devices based on semiconductor materials, including various types of diodes, transistors, field-effect transistors, and thyristors (the latter three are all three-terminal devices).
Transistors are semiconductor devices commonly used as amplifiers or electrically controlled switches. They serve as the fundamental building blocks for operating computers, mobile phones, and all other modern electronic circuits.
Due to their fast response speed and high accuracy, transistors can be used for a wide range of digital and analog functions, including amplification, switching, voltage regulation, signal modulation, and oscillation. Transistors can be individually packaged or integrated into a very small area, accommodating billions or more transistors as part of an integrated circuit.
In December 1947, a research team consisting of Shockley, Bardeen, and Brattain from Bell Laboratories in the United States developed a point-contact germanium transistor, marking a significant invention of the 20th century and heralding the advent of the microelectronics revolution. With the introduction of transistors, it became possible to replace bulky, power-consuming vacuum tubes with compact, low-power electronic devices. The invention of the transistor also paved the way for the subsequent development of integrated circuits. During the first ten years of the 20th century, semiconductor materials began to be utilized in communication systems, and mineral detectors using semiconductor materials gained popularity among radio enthusiasts in the first half of the 20th century. The electrical properties of semiconductors were also applied in telephone systems.
The earliest concept of the transistor can be traced back to 1929 when engineer Lilienfeld obtained a patent for a type of transistor. However, due to the technological limitations at the time, the materials required to manufacture such devices did not reach the necessary level of purity, making it impossible to produce these transistors.
Due to the unsatisfactory performance of vacuum tubes in handling high-frequency signals, efforts were made to improve the mineral detectors used in crystal radios. In these detectors, a fine wire contacted the surface of the mineral (semiconductor) to serve as a rectifying contact, allowing the current to flow in one direction while preventing it from flowing in the opposite direction. Just before the outbreak of World War II, Bell Laboratories discovered that germanium crystals doped with extremely small amounts of impurities outperformed galena crystals and even vacuum tube rectifiers in certain aspects when seeking superior detection materials.
During the Second World War, many laboratories made significant progress in the manufacturing and theoretical research of silicon and germanium materials, laying the groundwork for the invention of the transistor.
To overcome the limitations of vacuum tubes, after the end of World War II, Bell Laboratories intensified its basic research on solid-state electronic devices. Shockley and his colleagues focused on the possibility of using semiconductor materials such as silicon and germanium to create amplifier devices.
In the fall of 1945, a semiconductor research group led by Shockley was established at Bell Laboratories, with members including Brattain and Bardeen. Brattain had been working at the laboratory since 1929, dedicating himself to semiconductor research and accumulating extensive experience. Through Electronic Components of experiments and observations, they gradually realized the cause of the current amplification effect in semiconductors. Brattain discovered that when an electrode was placed on the bottom surface of a germanium wafer and a fine needle was inserted into the other side and a weak current was applied, a significant change in the original current would occur when the other fine needle was brought close to it and a weak current was passed through. The slight variation in the weak current would have a considerable impact on the other current, leading to an “amplification” effect.
Brattain and his colleagues also devised effective methods to achieve this amplification effect. They input a weak signal between the emitter and base and obtained a strong signal output between the collector and base. The amplification effect of the transistor’s three terminals is widely utilized in modern electronic products.
The initial amplification factor of the solid-state device produced by Bardeen and Brattain was around 50. Shortly thereafter, they replaced the gold foil contact with two closely spaced (0.05 mm apart) whisker contacts, creating the “point-contact transistor.” In December 1947, the world’s first practical semiconductor device was finally unveiled, capable of amplifying audio signals 100 times. It was shorter than a matchstick but slightly thicker.
When naming this device, Brattain considered its resistance-changing characteristics, as it operated by a transfer current from “low-resistance input” to “high-resistance output,” and thus named it the “trans-resistor,” later abbreviated to “transistor.”
Due to the complexity of the manufacturing process for point-contact transistors, many products experienced malfunctions, and they also suffered from drawbacks such as high noise, difficulty in control at high power, and narrow applicability. To overcome these shortcomings, Shockley proposed a bold idea to use a “PN junction” to replace the metal-semiconductor contact. The semiconductor research group also proposed the working principle of this semiconductor device.
In 1950, the first “PN junction transistor” was introduced, and its performance was entirely consistent with Shockley’s original conception (the so-called PN junction refers to the junction between P-type and N-type materials, where P-type has an abundance of holes and N-type has an abundance of electrons).
In 1956, Shockley, Bardeen, and Brattain were jointly awarded the Nobel Prize in Physics for the invention of the transistor.
In 2022, Professor Ren Tianling’s team at the Institute of Microelectronics of Tsinghua University developed a “sidewall” transistor using single-layer graphene as the gate, setting a record with a gate length of 0.34 nm. This research was published in the latest issue of Nature, titled “Vertical MoS2 transistors with sub-1-nm gate lengths.”
In 2023, Dutch scientists developed the first two-dimensional (2D) topological insulator made of single-element germanene, which can replace traditional transistors in electronic devices and eliminate heat generation.
What is a Transistors (electronic component)?
