Evidence for low diffusivity and mobility of minority carriers in highly doped Si and interpretation

Experimental evidence for low minority-carrier diffusivity and mobility in highly doped Si:As is presented and explained by a simple model. The model emphasizes the carrier transport, including trapping, in the tail states of the minority-carrier band that will influence the minority-carrier mobility and diffusivity while not influencing the majority-carrier transport. The measured values for minority holes in n+-Si:As layers with doping concentrations of about 1.5×1020 cm−3 are Dp≂0.2 cm2/s and μp≂6.3 cm2/Vs, which are about one order of magnitude smaller than the corresponding values for the majority holes. These new results pertain to device design and understanding of heavy doping effects and mechanisms.