4.4 Diffusion of Carriers
When excess carriers are created nonuniformly in a semiconductor, the electron and hole concentrations vary with position in the sample. Any such spatial variation (gradient) in n and p calls for a net motion of the carriers from regions of high carrier concentration to regions of low carrier concentration. This type of motion is called diffusion and represents an important charge transport process in semiconductors. The two basic processes of current conduction are diffusion due to a carrier gradient and drift in an electric field.
4.4.1 Diffusion Processes
When a bottle of perfume is opened in one corner of a closed room, the scent is soon detected throughout the room. If there is no convection or other net motion ...
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