ASSESSMENT OF INTERVALLEY F-SCATTERING TIME CONSTANTS IN SI SIGE HETEROSTRUCTURES/

The conduction band edge of silicon consists of six minima located in k-space along [100] directions. Transitions of electrons between perpe ndicular valleys are induced by so-called f-type intervalley scatterin g processes. In this work we have studied f-type intervalley scatterin g times using a specific Si/SiGe bipolar transistor test structure wer e (low effective mass) electrons are selectively injected into four of the six valleys split energetically apart from the other two valleys by lattice mismatch strain. From the observed dependence of the collec tor current on the base width f-scattering time constants are deduced.