Transport processes at interfaces
There are a number of processes unique to interfaces that can allow carriers to cross the boundary between two materials or between two grains. These processes are in series with the bulk transport mechanisms just discussed. In this section we focus on these interface transport mechanisms. A metal-semiconductor structure in forward bias is used in Figure Interface transport mechanisms illustrated using a forward-biased, metal-semiconductor junction. Path a is thermionic emission, path b is thermally enhanced field emission, path c is multistep tunneling, path d is field emission, path e involves trapping and subsequent emission, path f is interface recombination, and path g is minority-carrier injection.to illustrate them. From the figure it is seen that mechanisms a to e involve the semiconductor majority carriers, while mechanism f involves both majority and minority carriers. Mechanism g involves only minority carriers. Although here we discuss these mechanisms in the context of a metal-semiconductor contact, the general features of these various interface transport mechanisms will also be found at other interfaces.