Polysilicon Emitter p-n-p Transistors
In-situ boron-doped polysilicon has been used to form the emitter in p-n-p transistors. Various polysilicon deposition conditions, interface preparation treatments prior to deposition, and post-deposition anneals were investigated. Unannealed devices lacking a deliberately grown interfacial oxide gave effective emitter Gummel numbers ge of 7–9 × 1012 scm-4 combined with emitter resistances RE of approximately 8 μΩcm2. Introduction of a chemically grown interfacial oxide increased GE to 2 × 1014 scm-4, but also raised REby a factor of three. Annealing at 900°C following polysilicon deposition raised GEvalues for transistors lacking deliberate interfacial oxide to approximately 6 × 1013 scm-4, but had little effect on GE for devices with interfacial oxide. Both types of annealed devices gave RE values of range 1–2 μΩcm2.