Solid State Electronic Devices, 7th Edition

7.3 BJT Fabrication

The first transistor invented by Bardeen and Brattain in 1947 was the point contact transistor. In this device two sharp metal wires, or “cat’s whiskers,” formed an “emitter” of carriers and a “collector” of carriers. These wires were simply pressed onto a slab of Ge which provided a “base” or mechanical support, through which the injected carriers flowed. This basic invention rapidly led to the BJT, in which charge injection and collection was achieved using two p-n junctions in proximity to each other. The p-n junctions in BJTs can be formed in a variety of ways using thermal diffusion, but modern devices are generally made using ion implantation (Section 5.1.4).

Let us review a simplified version of how to make a double ...