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Alloy-junction transistor

January 01, 1970

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.

Close up view of the interior of an RCA 2N140 PNP Germanium Alloy Junction Transistor, circa 1953
Close up view of the interior of a General Electric 2N1307 PNP Germanium Alloy Junction Transistor, 1960s

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. Indium and antimony were commonly used to form the alloy junctions on a bar of N-type germanium. The collector junction pellet would be about 50 mils (thousandths of an inch) in diameter, and the emitter pellet about 20 mils. The base region would be on the order of 1 mil (0.001 inches, 25 μm) thick.[1] 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 they cost much less, and the characteristics of planar transistors improved very rapidly, quickly exceeding those of all earlier germanium transistors.

Micro-alloy transistor edit

The micro-alloy transistor (MAT) was developed by Philco 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.

Micro-alloy diffused transistor edit

The micro-alloy diffused transistor (MADT), or micro-alloy diffused-base transistor, was developed by Philco as an improved type of micro-alloy transistor; it offered even higher speed. It is a type of diffused-base transistor.

Before using electrochemical techniques and etching depression wells into the base semiconductor crystal material, a heated diffused phosphorus gaseous layer is created over the entire intrinsic semiconductor base crystal, creating a N-type graded base semiconductor material. 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 diffused base layer and through most of the intrinsic base semiconductor region, forming an extremely thin base region.[2][3] A doping-engineered electric field was created in the diffused base layer to reduce the charge carrier base transit time (similar to the drift-field transistor).

Post-alloy diffused transistor edit

The post-alloy diffused transistor (PADT), or post-alloy diffused-base transistor, was developed by Philips (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-engineered electric field was created in the diffused base layer to reduce the charge carrier base transit time (similar to the drift-field transistor).

Photo gallery edit

  •  
    TG 51 PNP germanium alloy transistor Made by TEWA Poland
  •  
    TG 51 PNP germanium alloy transistor Made by TEWA Poland
  •  
    General Electric 2N1307 PNP germanium alloy transistor
  •  
    General Electric 2N1307 PNP germanium alloy transistor
  •  
    RCA 2N404 Germanium PNP Transistor. Medium Speed Switch
  •  
    PNP germanium alloy transistor intended as AF amplifier / switch


See also edit

References edit

  1. ^ Lloyd P. Hunter (ed.), Handbook of Semiconductor Electronics, Mc Graw Hill, 1956 pp. 7–18, 7–19
  2. ^ A High Frequency Transistor Analysis by James K. Keihner, 1956
  3. ^ Wall Street Journal, Article: "Philco Says It Is Producing A New Kind Of Transistor", October 9, 1957, pg 19

External links edit

  • Manufacture of Junction Transistors

January 01, 1970
alloy, junction, transistor, germanium, alloy, junction, transistor, alloy, transistor, early, type, bipolar, junction, transistor, developed, general, electric, 1951, improvement, over, earlier, grown, junction, transistor, close, view, interior, 2n140, germa. 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 Close up view of the interior of an RCA 2N140 PNP Germanium Alloy Junction Transistor circa 1953 Close up view of the interior of a General Electric 2N1307 PNP Germanium Alloy Junction Transistor 1960s 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 Indium and antimony were commonly used to form the alloy junctions on a bar of N type germanium The collector junction pellet would be about 50 mils thousandths of an inch in diameter and the emitter pellet about 20 mils The base region would be on the order of 1 mil 0 001 inches 25 mm thick 1 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 they cost much less and the characteristics of planar transistors improved very rapidly quickly exceeding those of all earlier germanium transistors Contents 1 Micro alloy transistor 2 Micro alloy diffused transistor 3 Post alloy diffused transistor 4 Photo gallery 5 See also 6 References 7 External linksMicro alloy transistor editThe micro alloy transistor MAT was developed by Philco 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 Micro alloy diffused transistor editThe micro alloy diffused transistor MADT or micro alloy diffused base transistor was developed by Philco as an improved type of micro alloy transistor it offered even higher speed It is a type of diffused base transistor Before using electrochemical techniques and etching depression wells into the base semiconductor crystal material a heated diffused phosphorus gaseous layer is created over the entire intrinsic semiconductor base crystal creating a N type graded base semiconductor material 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 diffused base layer and through most of the intrinsic base semiconductor region forming an extremely thin base region 2 3 A doping engineered electric field was created in the diffused base layer to reduce the charge carrier base transit time similar to the drift field transistor Post alloy diffused transistor editThe post alloy diffused transistor PADT or post alloy diffused base transistor was developed by Philips 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 engineered electric field was created in the diffused base layer to reduce the charge carrier base transit time similar to the drift field transistor Photo gallery edit nbsp TG 51 PNP germanium alloy transistor Made by TEWA Poland nbsp TG 51 PNP germanium alloy transistor Made by TEWA Poland nbsp General Electric 2N1307 PNP germanium alloy transistor nbsp General Electric 2N1307 PNP germanium alloy transistor nbsp RCA 2N404 Germanium PNP Transistor Medium Speed Switch nbsp PNP germanium alloy transistor intended as AF amplifier switchSee also editTetrode transistorReferences edit Lloyd P Hunter ed Handbook of Semiconductor Electronics Mc Graw Hill 1956 pp 7 18 7 19 A High Frequency Transistor Analysis by James K Keihner 1956 Wall Street Journal Article Philco Says It Is Producing A New Kind Of Transistor October 9 1957 pg 19External links editManufacture of Junction Transistors Retrieved from https en wikipedia org w index php title Alloy junction transistor amp oldid 1140632026 Post alloy diffused transistor, wikipedia, wiki, book, books, library,

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