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.
