Diffused junction transistor: Difference between revisions

Revision as of 17:18, 10 January 2016

Revision as of 17:22, 10 January 2016

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==Double diffusion==

At Bell Labs [[Calvin Souther Fuller]] produced basic physical understanding of a means of directly forming the [[emitter, base, and collector]] by double diffusion. The method was summarized in 1983 in a history of science at Bell:<ref>Millman (1983) p 426</ref>

:Fuller had shown that [[acceptor (semiconductors)|acceptor]]s of low [[atomic weight]] diffuse more rapidly than [[donor (semiconductors)|donor]]s, which made possible n&ndash;p&ndash;n structures by simultaneous diffusion of donors and acceptors of appropriately different surface concentrations. The first n&ndash;layer (the emitter) was formed because of the greater surface concentration of the donor (for example, [[antimony]]). The base formed beyond it because of the more rapid diffusion of the acceptor (for example, [[aluminum]]). The inner (collector) boundary of the base appeared where the diffused aluminum no longer over-compensated the n&ndash;type background doping of the original [[silicon]]. The base layers of the resulting transistors were 4 μm thick. ... Resulting transistors had a [[cut-off frequency]] of 120 MHz.