what is a pn diode? how is it obtained?

when we join p type and n type semiconductors together, pn jn diode is formed. it allows  current to flow in forward bias(ie when p connected to positive and n connected to negative) and stops current through it in reverse bias.so it works like a valve. this pn diode is very useful for various useful operations.

here in this diode we can control current by varying the output voltage.

now p type semiconductor is obtained by adding impurity of pentavalent atom in the pure semiconductor(say si). so there we get enough free electrons which can flow if pd is applied.

n type semiconductor we get by adding impurity of trivalent atoms in pure semiconductors. so thetre will be defficiency of electrons called holes.which move when pd is applied.