Talk:Alloy-junction transistor

Article is Innacurate, needs rewrite. First this article is only applicable to Germanium transistors Only. I have these transistors. I have taken off the top of the metal can to confirm that the germanium structure. Etching features into Germanium tranistors was not done because of the different chemistry of Germanium vs Silicon et al. The thin Germanium wafers were made by depositing unto salt crystals (to force orientaion)then washing away the salt, not something one can do with Silicon. The earlier plated junction transistors are schotky metal to semiconductor junctions like point contact transistors. Metal Alloy Dot transistors "made from a wafer of N-type germanium 6 mils thick. Indium dots that would create the emitter and collector were fixed to either side of the wafer and alloyed by heating the assembly in an oven under strict temperature control. On heating about 2 mils of the germanium was dissolved by the molten indium on each side and on cooling the germanium recrystallised as P-type creating a PNP structure between the indium dots. The residual N-type layer now 2 mils thick became the base." "The alloy junction transistor was invented by John Saby at General Electric and similar developments were undertaken by Jacques Pankove at RCA. Inventorship had to be established in the US Courts as RCA filed on Pankove’s work one day ahead of General Electric in June 1952. They were initially PNP types and commenced with a wafer of N-type germanium, typically doped with antimony which became the base. Some details of production are set out in Pankove’s patent [Pankove 1952]. The transistor base is made from doped mono-crystalline germanium typically of 2-5 ohm-cm and of N-Type for PNP transistors. The crystal is diced into wafers and then acid etched to remove surface defects caused by dicing. The etched wafer are 3-6 mils in thickness. Indium dots are prepared 10 mils thick and 15 mil for the emitter and 80 mil for the collector (mil = 1/1000 inch). The collector dot is applied first and adhered by firing at 250C for one minute The emitter dot is applied and the wafer fired at 400-500C for 10-20 minutes. The firing process is enough to melt the indium which alloys with the germanium. The alloy has a lower melting point than pure germanium and two molten puddles of alloy form under the indium dots. On cooling the germanium alloy re-crystalises and re-forms a single crystal. As indium is an acceptor P-type regions form under the indium dots creating the PNP structure. By managing the wafer thickness and the alloying time the width of the base region can be controlled."

Refs

Gottlieb E Gutzwiller F Jones D Lowry H Snyder G Stasior R Sylvan T 1959 General Electric Transistor Manual Fourth Edition

Hall R 1952 P-N Junctions Produced by Growth Rate Variation Phys Rev 88 139

Lesk I Gonzalez R 1957 High-frequency transistors by the diffused-meltback process employing three impurities Electron Devices Meeting, 1957 International 3 117

Pankove J 1952 US Patent 3005132 Transistors Filed 13th June 1952 Patented 17th October 1961

Shockley W Sparks M Teal G 1951 P-N Junction Transistors Phys Rev 83 151-62

Shockely W 1976 The Path to the Conception of the Junction Transistor IEEE Trans on Electron Devices ED-23 July 597-620

Shjacks45 (talk) 01:57, 9 February 2010 (UTC)