ABSTRACT
How high a performance can be achieved in silicon-based bipolar transistors? An answer to such a question
surely considers many assumptions. New discoveries continue to affect the critical aspects of device
operation such as charge storage, carrier transport, and parasitics. Other discoveries affect the processing
of the device, leading to even better ways to make the device structurally ideal. One example of a historic
discontinuity in device fabrication and operation is the development of production-ready SiGe epitaxy.
Before the advent of SiGe epitaxy, predictions toward device limits would likely have made certain
assumptions regarding emitter charge storage or minority carrier diffusion and this would clearly be off
the mark due to the significant advancement in SiGe band engineering. More recently, the incorporation of
carbon has provided a boost, strongly affecting the diffusion of dopants and thus providing a greater control
over the device structure. Similar innovations are expected to continue to provide a boost to the device
operation, and so continually change the assumptions that may go into predicting limits of device operation.
