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Line 8: ==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–p–n structures by simultaneous diffusion of donors and acceptors of appropriately different surface concentrations. The first n–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–type background doping of the original [[silicon]]. The base layers of the resulting transistors were 4 μm thick. ... Resulting ~~transitors~~transistors had a [[cut-off frequency]] of 120 MHz. ==Mesa transistor==

Diffused junction transistor: Difference between revisions