Poly-crystalline silicon-carbide (SiCarb) emitter bipolar transistors

The use of polycrystalline silicon-carbide (SiCarb) as a wide bandgap emitter for bipolar transistors is investigated. The SiCarb is deposited in a modified LPCVD reactor with propane used as the carbon source gas, giving carbon concentrations of 4, 8, 16, and 18%. Doping of the emitter layers is achieved either by arsenic implantation into he undoped layers or by the use of in situ phosphorus doped layers, together with a rapid thermal emitter anneal. The 4 and 8% SiCarb devices show a factor of 2.5 reduction in base current compared to a polysilicon control, while the 16 and 18% SiCarb devices show a factor of 2.8 increase in base current compared to a polysilicon control. Modeling of these devices indicates that the base currents are dominated by poly-emitter effects such as a low mobility in the deposited SiCarb layers and recombination at the SiCarb/monosilicon interface, rather than by any wide bandgap emitter effects.<
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