Alloy-junction transistor
Encyclopedia
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
.
The usual construction of an alloy-junction transistor is a germanium
crystal forming the base, with emitter and collector alloy beads fused on opposite sides. There were several types of improved alloy-junction transistors developed over the years that they were manufactured.
All types of alloy-junction transistors became obsolete in the early 1960s, with the introduction of the planar transistor which could be mass produced easily while alloy-junction transistors had to be made individually. The first germanium planar transistors had much worse characteristics than alloy-junction germanium transistors of the period, but as they could be mass produced and alloy-junction transistors could not, they cost much less and the characteristics of planar transistors improved very rapidly, quickly exceeding those of all earlier Germanium transistors.
as an improved type of alloy-junction transistor, it offered much higher speed.
It is constructed of a semiconductor crystal forming the base, into which a pair of wells are etched (similar to Philco's earlier surface-barrier transistor
) on opposite sides then fusing emitter and collector alloy beads into the wells.
(but GE and RCA filed for patent and Jacques Pankove of RCA received patent for it) as an improved type of micro-alloy transistor; it offered even higher speed. It is a type of diffused-base transistor.
Before etching wells into the base crystal, a diffused base layer is created over the entire base crystal. The emitter well is etched very shallow into this diffused base layer.
For high-speed operation, the collector well is etched all the way through the intrinsic base semiconductor to the diffused base layer. A doping-engineer
ed electric field
was created in the diffused base layer to reduce the charge carrier
base transit time (similar to the drift-field transistor
).
For high-voltage operation, the collector well is not etched all the way to the diffused base layer, leaving some intrinsic base semiconductor.
(but GE and RCA filed for patent and Jacques Pankove of RCA received patent for it) as an improvement to the germanium alloy-junction transistor, it offered even higher speed. It is a type of diffused-base transistor.
The Philco micro-alloy diffused transistor had a mechanical weakness that ultimately limited their speed; the thin diffused base layer would break if made too thin, but to get high speed it needed to be as thin as possible. Also it was very hard to control alloying on both sides of such a thin layer.
The post-alloy diffused transistor solved this problem by making the bulk semiconductor crystal the collector (instead of the base), which could be as thick as necessary for mechanical strength. The diffused base layer was created on top of this. Then two alloy beads, one P-type and one N-type were fused on top of the diffused base layer. The bead having the same type as the base dopant then became part of the base and the bead having the opposite type from the base dopant became the emitter.
A doping-engineer
ed electric field
was created in the diffused base layer to reduce the charge carrier
base transit time (similar to the drift-field transistor
).
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...
, developed at General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
and RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
in 1951 as an improvement over the earlier grown-junction transistor
Grown-junction transistor
The grown-junction transistor was the first type of bipolar junction transistor made. It was invented by William Shockley at Bell Labs on June 23, 1948. The patent was filed on June 26, 1948. The first germanium prototypes were made in 1949...
.
The usual construction of an alloy-junction transistor is a germanium
Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....
crystal forming the base, with emitter and collector alloy beads fused on opposite sides. There were several types of improved alloy-junction transistors developed over the years that they were manufactured.
All types of alloy-junction transistors became obsolete in the early 1960s, with the introduction of the planar transistor which could be mass produced easily while alloy-junction transistors had to be made individually. The first germanium planar transistors had much worse characteristics than alloy-junction germanium transistors of the period, but as they could be mass produced and alloy-junction transistors could not, they cost much less and the characteristics of planar transistors improved very rapidly, quickly exceeding those of all earlier Germanium transistors.
Micro-alloy transistor
The micro-alloy transistor (MAT) was developed by PhilcoPhilco
Philco, the Philadelphia Storage Battery Company , was a pioneer in early battery, radio, and television production as well as former employer of Philo Farnsworth, inventor of cathode ray tube television...
as an improved type of alloy-junction transistor, it offered much higher speed.
It is constructed of a semiconductor crystal forming the base, into which a pair of wells are etched (similar to Philco's earlier surface-barrier transistor
Surface-barrier transistor
The surface-barrier transistor is a type of transistor developed by Philco in 1953 as an improvement to the alloy-junction transistor and the earlier point-contact transistor...
) on opposite sides then fusing emitter and collector alloy beads into the wells.
Micro-alloy diffused transistor
The micro-alloy diffused transistor (MADT), or micro-alloy diffused-base transistor, was developed by PhilcoPhilco
Philco, the Philadelphia Storage Battery Company , was a pioneer in early battery, radio, and television production as well as former employer of Philo Farnsworth, inventor of cathode ray tube television...
(but GE and RCA filed for patent and Jacques Pankove of RCA received patent for it) as an improved type of micro-alloy transistor; it offered even higher speed. It is a type of diffused-base transistor.
Before etching wells into the base crystal, a diffused base layer is created over the entire base crystal. The emitter well is etched very shallow into this diffused base layer.
For high-speed operation, the collector well is etched all the way through the intrinsic base semiconductor to the diffused base layer. A doping-engineer
Doping (semiconductor)
In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor for the purpose of modulating its electrical properties. The impurities are dependent upon the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic...
ed electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
was created in the diffused base layer to reduce the charge carrier
Charge carrier
In physics, a charge carrier is a free particle carrying an electric charge, especially the particles that carry electric currents in electrical conductors. Examples are electrons and ions...
base transit time (similar to the drift-field transistor
Drift-field transistor
The drift-field transistor, also called the drift transistor or graded base transistor, is a type of high-speed bipolar junction transistor having a doping-engineered electric field in the base to reduce the charge carrier base transit time....
).
For high-voltage operation, the collector well is not etched all the way to the diffused base layer, leaving some intrinsic base semiconductor.
Post-alloy diffused transistor
The post-alloy diffused transistor (PADT), or post-alloy diffused-base transistor, was developed by PhilipsPhilips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
(but GE and RCA filed for patent and Jacques Pankove of RCA received patent for it) as an improvement to the germanium alloy-junction transistor, it offered even higher speed. It is a type of diffused-base transistor.
The Philco micro-alloy diffused transistor had a mechanical weakness that ultimately limited their speed; the thin diffused base layer would break if made too thin, but to get high speed it needed to be as thin as possible. Also it was very hard to control alloying on both sides of such a thin layer.
The post-alloy diffused transistor solved this problem by making the bulk semiconductor crystal the collector (instead of the base), which could be as thick as necessary for mechanical strength. The diffused base layer was created on top of this. Then two alloy beads, one P-type and one N-type were fused on top of the diffused base layer. The bead having the same type as the base dopant then became part of the base and the bead having the opposite type from the base dopant became the emitter.
A doping-engineer
Doping (semiconductor)
In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor for the purpose of modulating its electrical properties. The impurities are dependent upon the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic...
ed electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
was created in the diffused base layer to reduce the charge carrier
Charge carrier
In physics, a charge carrier is a free particle carrying an electric charge, especially the particles that carry electric currents in electrical conductors. Examples are electrons and ions...
base transit time (similar to the drift-field transistor
Drift-field transistor
The drift-field transistor, also called the drift transistor or graded base transistor, is a type of high-speed bipolar junction transistor having a doping-engineered electric field in the base to reduce the charge carrier base transit time....
).