Nonequilibrium Electron Dynamics in Small Semiconductor Structures.

Reducing length scales in n-p-n heterojunction bipolar transistors leads to changes in both the mode of operation and the fundamental limits to device performance. For example, extreme nonequilibrium electron motion dominates base transport when device base thickness is similar to the characteristics mean free path of charge carriers. In addition, changes in scattering phase space can result in reduced inelastic electron rates at very high p-type carrier concentration. Although we now have a qualitative understanding of the physics of operation of the fastest bipolar transistors, some important questions remain concerning the correct description of elastic and inelastic scattering in small heterojunction structures.