Mandeep asks:

“As we take a negative charge on the electron,when
electron leave there position,the left particle is
hole,my question is that why we consider hole as a
positive charge ,as a hole is a efficiency of
electron not containing any charge”

 

Answer: Hole is the deficiency (not efficiency) of an electron. It is assigned a positive charge for the sake of convenience of discussing it like a moving charge. When an electron leaves a site, the atom gets ionized and gets a positive charge. This is actually caused by the deficiency of electron. SO, we treat the vacancy of electron like a mobile positive charge. When an electron from the neighbouring atom leaves its ste and another electron fill a hole previously present, we treat it as if the hole has moved from one site to another.

Links:

• http://britneyspears.ac/physics/basics/basics.htm
• http://ecee.colorado.edu/~bart/book/eband4.htm
• http://hyperphysics.phy-astr.gsu.edu/hbase/solids/intrin.html