p- n type semiconductor

p-type In a pure (intrinsic) Si or Ge semiconductor, each nucleus uses its four valence electrons to form four covalent bonds with its neighbors (see figure below). the nucleus and non-valent electrons, has a net charge of +4, and is surrounded by 4 valence electrons.the number of electrons and holes present at any given time will always be equal.

a semiconductor that has been doped with an acceptor is called a p-type semiconductor; "p" stands for positiveIn a p-type semiconductor, current is largely carried by the holes, which outnumber the free electrons. In this case, the holes are the majority carriers, while the electrons are the minority carriers.

n- type semiconductor Provides a large number of free electrons . n type semiconductors are known as donor impurities because the donate free electrons to the semiconductor.Donor impurities donate 

negatively charged electrons to the lattice, so a semiconductor that has been doped with a donor is called an n-type semiconductor; "n" stands for negative. Free electrons outnumber holes in an n-type material, so the electrons are the majority carriers and holes are the minority carriers