Arsenic-doped emitters have been shown to produce high performance in bipolar silicon transistors. In comparison with phosphorus, the emitter dopant commonly used in the industry, the use of arsenic results in a steeper gradient (1024/cm4), less compensation of the base region, no “emitter dip” effect, and a flatter profile with higher sheet conductivity. Since arsenic atoms are a better match to Si than are phosphorus atoms and the arsenic process requires lower surface concentration for a particular diffusion depth and sheet conductivity, fewer crystal defects are generated. As a result the arsenic emitter process results in a higher device yield and is much more reproducible, even for shallow diffusion depths. Arsenic-emitter transistors, both with and without gold doping, are found to be superior in performance, with 1.6 to 2 times higher gain bandwidth, ƒT and current gain, β, than those with phosphorus emitters with similar geometry. Also the ability of the arsenic emitter to sustain large current densities, exceeding 30,000 A-cm−2, makes it extremely desirable for high density, small geometry, and high-performance silicon devices.
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