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9.9 P-N Junctions
We can have, then, p-type material, in which conduction is by holes
(positive carriers); η-type, in which it is by electrons (negative
carriers); and what is sometimes called i-type (for 'intrinsic'), in
which it is by both in equal numbers. None of these by itself is
particularly useful; it is when more than one kind are in contact that
interesting things begin to happen. Just bringing two pieces together
is not good enough, however; the combination has to be in one
crystalline piece, divided into two or more regions having different
impurities. Various manufacturing methods have been devised for
achieving this. The proces ...