Multilayer heterojunction bipolar transistor wafer

Fig. 27.12 Typical components in a multilayer heterojunction bipolar transistor wafer, each deposited by CVD.

Mobile telephones incorporate multilayer III-V epitaxial heterojunction bipolar transistor wafers such as that illustrated in Figure 27.12. The p-n junctions on either side of the base layer are a crucial feature of semiconductor devices, and in the wafer shown in Figure 27.12 (and in other similar wafers), the p-type base layer must be highly doped to provide high-frequency performance. Choice of dopant is critical, e.g. use of a Zn dopant (see below) results in its diffusion into the emitting n-type layers. This problem has been overcome by doping with C which exhibits a low diffusion coefficient C-doped wafers have been used commercially since the early 1990s. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

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