Now p-type impurities are diffused which form the base of the transistor. This path acts as a collector of the transistor. In this technique, a very thin and high Purity single crystal layer of n-type silicon is grown on a heavily doped substrate of the same material. n-type impurities after passing through the Aperture deposit over the base and from the n-type layer which acts as the emitter of the transistor.Ī silicon dioxide layer is Grown over the surface and then photoetched in order to make aluminum contacts for both the emitter and base leads.

This system is now heated in the gaseous environment of n-type impurities. Now the system is covered with a mask having a small aperture over the base region. The flat surface of the wafer acts as a collector. p-type impurities diffuse into the wafer surface and form the base of the transistor. Similarly, the NPN transistor can also be manufactured.Ī flat wafer surface of n-type Silicon (known as n-type substrates) is heated in a furnace having p-type impurities in the gaseous form. Thus, both the side of the wafer becomes p-type whereas the middle part of the wafer is n-type which acts as the base of the PNP transistor. The Indium melt and penetrates little in the wafer.

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