How P-Type Silicon is created:
To make P-Type silicon, trivalent impurities are added or mixed with Silicon (Si), so before going forward have a look on trivalent impurities. Boron, Indium, Aluminum and Gallium have three valence electrons so these are called trivalent impurities.
When we mix boron or when boron is added to Silicon (Si), every atom of boron (three electrons) are looked up in covalent bond with the valence electrons of neighboring Silicon electrons. During this process of bonding, a vacant hole is created within the covalent bond between one boron atom and a neighboring Silicon (Si) atom. The holes are considered to be positive charge carriers.
When a voltage is applied across the silicon-boron mixture, a hole moves toward the negative voltage end while a neighboring electron fills in its place. When boron is added to Si to yield the above effect, we say that Si is doped with boron. The resulting mixture is called P-type silicon (P: positive charge carrier silicon).
Graphic Representation of all above shown process is given below in diagram
Points to Remember are:
- The hole of boron atom points towards the negative terminal.
- The electron of neighboring silicon atom points toward positive terminal.
- The electron from neighboring silicon atom falls into the boron atom filling the hole in boron atom and creating a “new” hole in the silicon atom.
- It appears as though a hole moves toward the negative terminal.