Grown-junction transistor

Last updated
A silicon NPN grown-junction transistor with the cover removed to show the silicon ingot and the base wire. Grown-junction NPN transistor type ST2010.png
A silicon NPN grown-junction transistor with the cover removed to show the silicon ingot and the base wire.

The grown-junction transistor was the first type of bipolar junction transistor made. [1] It was invented by William Shockley at Bell Labs on June 23, 1948 [2] (patent filed June 26, 1948), six months after the first bipolar point-contact transistor. The first germanium prototypes were made in 1949. Bell Labs announced Shockley’s grown-junction transistor on July 4, 1951.

Bipolar junction transistor transistor that uses both electron and hole charge carriers.In contrast,unipolar transistors such as field-effect transistors,only use one kind of charge carrier.For their operation,BJTs use 2 junctions between 2 semiconductor types,n-type and p-type

A bipolar junction transistor is a type of transistor that uses both electron and hole charge carriers. In contrast, unipolar transistors, such as field-effect transistors, only use one kind of charge carrier. For their operation, BJTs use two junctions between two semiconductor types, n-type and p-type.

William Shockley American physicist and inventor

William Bradford Shockley Jr. was an American physicist and inventor. Shockley was the manager of a research group at Bell Labs that included John Bardeen and Walter Brattain. The three scientists were jointly awarded the 1956 Nobel Prize in Physics for "their researches on semiconductors and their discovery of the transistor effect".

Bell Labs research and scientific development company

Nokia Bell Labs is an industrial research and scientific development company owned by Finnish company Nokia. Its headquarters are located in Murray Hill, New Jersey. Other laboratories are located around the world. Bell Labs has its origins in the complex past of the Bell System.

Contents

An NPN grown-junction transistor is made of a single crystal of semiconductor material which has two PN junctions grown into it. During the growth process, a seed crystal is slowly pulled from a bath of molten semiconductor, which then grows into a rod-shaped crystal (boule). The molten semiconductor is doped N-type at the start. At a predetermined moment in the growth process a small pellet of a P-type dopant is added, almost immediately followed by a somewhat larger pellet of an N-type dopant. These dopants dissolve in the molten semiconductor changing the type of semiconductor subsequently grown. The resulting crystal has a thin layer of P-type material sandwiched between sections of N-type material. This P-type layer may be as little as a thousandth of an inch thick. The crystal is sliced, leaving the thin P-type layer in the center of the slice, then cut into bars. Each bar is made into a transistor by soldering its N-type ends to supporting and conducting leads, then welding a very fine gold lead to the central P-type layer, and finally encasing in a hermetically sealed can. A similar process, using the opposite dopants, makes a PNP grown-junction transistor.

Crystal solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three spatial dimensions

A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.

A semiconductor material has an electrical conductivity value falling between that of a metal, like copper, gold, etc. and an insulator, such as glass. Their resistance decreases as their temperature increases, which is behaviour opposite to that of a metal. Their conducting properties may be altered in useful ways by the deliberate, controlled introduction of impurities ("doping") into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Some examples of semiconductors are silicon, germanium, and gallium arsenide. After silicon, gallium arsenide is the second most common semiconductor used in laser diodes, solar cells, microwave frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.

Seed crystal small piece of a single crystal

A seed crystal is a small piece of single crystal or polycrystal material from which a large crystal of typically the same material is to be grown in a laboratory. Used to replicate material, the use of seed crystal to promote growth avoids the otherwise slow randomness of natural crystal growth and allows manufacture on a scale suitable for industry.

The most difficult part of this process is welding the gold wire to the base layer, as the wire may have a larger diameter than the thickness of the base. To facilitate this operation, the gold wire is pointed or flattened until the end is thinner than the base layer. The tip of the gold wire is slid along the bar until electrical resistance measurement shows it is in contact with the base layer. At this time a pulse of current is applied, welding the wire in place. Unfortunately sometimes the weld is too large or slightly off center in the base layer. To avoid shorting the transistor, the gold wire is alloyed with a small amount of the same type dopant as used in the base. This causes the base layer to become slightly thicker at the point of the weld.

Grown-junction transistors rarely operated at frequencies above the audio range, due to their relatively thick base layers. Growing thin base layers was very hard to control and welding the wire to the base became harder the thinner it got. Higher-frequency operation could be obtained by welding a second wire on the opposite side of the base, making a tetrode transistor, and using special biasing on this second base connection.

A tetrode transistor is any transistor having four active terminals.

See also

Related Research Articles

Semiconductor device fabrication process used to create the integrated circuits that are present in everyday electrical and electronic devices

Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photolithographic and chemical processing steps during which electronic circuits are gradually created on a wafer made of pure semiconducting material. Silicon is almost always used, but various compound semiconductors are used for specialized applications.

Transistor semiconductor device used to amplify and switch electronic signals and electrical power

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

A semiconductor device is an electronic components that exploit the electronic properties of semiconductor material, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced vacuum tubes in most applications. They use electrical conduction in the solid state rather that the gaseous state or thermionic emission in a vacuum.

Gallium arsenide chemical compound

Gallium arsenide (GaAs) is a compound of the elements gallium and arsenic. It is a III-V direct bandgap semiconductor with a zinc blende crystal structure.

p–n junction semiconductor–semiconductor junction, formed at the boundary between a p-type and n-type semiconductor

A p–n junction is a boundary or interface between two types of semiconductor materials, p-type and n-type, inside a single crystal of semiconductor. The "p" (positive) side contains an excess of holes, while the "n" (negative) side contains an excess of electrons in the outer shells of the electrically neutral atoms there. This allows electrical current to pass through the junction only in one direction. The p-n junction is created by doping, for example by ion implantation, diffusion of dopants, or by epitaxy. If two separate pieces of material were used, this would introduce a grain boundary between the semiconductors that would severely inhibit its utility by scattering the electrons and holes.

High-electron-mobility transistor

A High-electron-mobility transistor (HEMT), also known as heterostructure FET (HFET) or modulation-doped FET (MODFET), is a field-effect transistor incorporating a junction between two materials with different band gaps as the channel instead of a doped region. A commonly used material combination is GaAs with AlGaAs, though there is wide variation, dependent on the application of the device. Devices incorporating more indium generally show better high-frequency performance, while in recent years, gallium nitride HEMTs have attracted attention due to their high-power performance. Like other FETs, HEMTs are used in integrated circuits as digital on-off switches. FETs can also be used as amplifiers for large amounts of current using a small voltage as a control signal. Both of these uses are made possible by the FET’s unique current-voltage characteristics. HEMT transistors are able to operate at higher frequencies than ordinary transistors, up to millimeter wave frequencies, and are used in high-frequency products such as cell phones, satellite television receivers, voltage converters, and radar equipment. They are widely used in satellite receivers, in low power amplifiers and in the defense industry.

In semiconductor production, doping is the intentional introduction of impurities into an intrinsic semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor. A semiconductor doped to such high levels that it acts more like a conductor than a semiconductor is referred to as a degenerate semiconductor.

Shockley Semiconductor Laboratory laboratory

Shockley Semiconductor Laboratory was a pioneering semiconductor developer founded by William Shockley as a division of Beckman Instruments, Inc., in 1956. It was the first high technology company in what came to be known as Silicon Valley to work on silicon-based semiconductor devices.

The heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) which uses differing semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle signals of very high frequencies, up to several hundred GHz. It is commonly used in modern ultrafast circuits, mostly radio-frequency (RF) systems, and in applications requiring a high power efficiency, such as RF power amplifiers in cellular phones. The idea of employing a heterojunction is as old as the conventional BJT, dating back to a patent from 1951. Detailed theory of heterojunction bipolar transistor was developed by Herbert Kroemer in 1957.

Point-contact transistor first type of solid-state electronic transistor ever constructed

The point-contact transistor was the first type of transistor to be successfully demonstrated. It was developed by research scientists John Bardeen and Walter Brattain at Bell Laboratories in December 1947. They worked in a group led by physicist William Shockley. The group had been working together on experiments and theories of electric field effects in solid state materials, with the aim of replacing vacuum tubes with a smaller device that consumed less power.

An extrinsic semiconductor is one that has been doped; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal, which is called an intrinsic semiconductor. In an extrinsic semiconductor it is these foreign dopant atoms in the crystal lattice that mainly provide the charge carriers which carry electric current through the crystal. The doping agents used are of two types, resulting in two types of extrinsic semiconductor. An electron donor dopant is an atom which, when incorporated in the crystal, releases a mobile conduction electron into the crystal lattice. An extrinsic semiconductor which has been doped with electron donor atoms is called an n-type semiconductor, because the majority of charge carriers in the crystal are negative electrons. An electron acceptor dopant is an atom which accepts an electron from the lattice, creating a vacancy where an electron should be called a hole which can move through the crystal like a positively charged particle. An extrinsic semiconductor which has been doped with electron acceptor atoms is called a p-type semiconductor, because the majority of charge carriers in the crystal are positive holes.

Alloy-junction transistor


The germanium alloy-junction transistor, or alloy transistor, was an early type of bipolar junction transistor, developed at General Electric and RCA in 1951 as an improvement over the earlier grown-junction transistor.

A diffusion transistor is a bipolar junction transistor (BJT) formed by diffusing dopants into a semiconductor substrate. The diffusion process was developed later than the alloy junction and grown junction processes for making BJTs.

A transistor is a semiconductor device with at least three terminals for connection to an electric circuit. The vacuum-tube triode, also called a (thermionic) valve, was the transistor's precursor, introduced in 1907.

John N. Shive American physicist

John Northrup Shive was an American physicist and inventor. He made notable contributions in electronic engineering and solid-state physics during the early days of transistor development at Bell Laboratories. In particular, he produced experimental evidence that holes could diffuse through bulk germanium, and not just along the surface as previously thought. This paved the way from Bardeen and Brattain's point-contact transistor to Shockley's more-robust junction transistor. Shive is best known for inventing the phototransistor in 1948, and for the Shive wave machine in 1959.

Morris Tanenbaum is an American physical chemist and executive who has worked at Bell Laboratories and AT&T Corporation.

References

  1. TRANSISTOR MUSEUM Historic Transistor Photo Gallery BELL LABS TYPE M1752
  2. Morris, Peter Robin (1990). "4.2". A History of the World Semiconductor Industry. IEE History of Technology Series 12. London: Peter Peregrinus Ltd. p. 29. ISBN   0-86341-227-0.