Carrier concentration in n type semiconductor

Majority & minority carriers

What is charge carrier?

Generally, carrier refers to any object that carry another object from one place to another place. For example, in countries such as India, Singapore and Brazil: Tiffin box or Tiffin carriers are widely used for carrying food from one place to another place. Here, the Tiffin box acts as a carrier that carries the food from one place to another place.

Let us take another example; People use vehicles such as buses, trains, airplanes, etc. to travel from one place to another place. Here, the vehicles act as carriers that carry people from one place to another place. In the similar way, particles such as free electrons and holes carry the charge or electric current from one place to another place. 

Negative charge carriers

The negative charge carriers such as free electrons are the charge carriers that carry negative charge with them while moving from one place to another place. Free electrons are the electrons that are detached from the parent atom and moves freely from one place to another place.

        

Positive charge carriers

The positive charge carriers such as holes are the charge carriers that carry positive charge with them while moving from one place to another place. Holes are the vacancies in valence band that moves from one place to another place within the valence band. 

Majority and minority charge carriers definition

The charge carriers that are present in large quantity are called majority charge carriers. The majority charge carriers carry most of the electric charge or electric current in the semiconductor. Hence, majority charge carriers are mainly responsible for electric current flow in the semiconductor.

The charge carriers that are present in small quantity are called minority charge carriers. The minority charge carriers carry very small amount of electric charge or electric current in the semiconductor.

 Charge carriers in intrinsic semiconductor

The semiconductors that are in pure form are called intrinsic semiconductors. In intrinsic semiconductor the total number of negative charge carriers (free electrons) is equal to the total number of positive charge carriers (holes or vacancy).

Total negative charge carriers = Total positive charge carriers

Majority and minority charge carriers in n-type semiconductor

When the pentavalent atoms such as Phosphorus or Arsenic are added to the intrinsic semiconductor, an n-type semiconductor is formed. In n-type semiconductor, large number of free electrons is present. Hence, free electrons are the majority charge carriers in the n-type semiconductor. The free electrons (majority charge carriers) carry most of the electric charge or electric current in the n-type semiconductor.

In n-type semiconductor, very small number of holes is present. Hence, holes are the minority charge carriers in the n-type semiconductor. The holes (minority charge carriers) carry only a small amount of electric charge or electric current in the n-type semiconductor. 

The total number of negative charge carriers (free electrons) in n-type semiconductor is greater than the total number of positive charge carriers (holes) in the n-type semiconductor.

Total negative charge carriers > Total positive charge carriers

Majority and minority charge carriers in p-type semiconductor

When the trivalent atoms such as Boron or Gallium are added to the intrinsic semiconductor, a p-type semiconductor is formed. In p-type semiconductor, large number of holes is present. Hence, holes are the majority charge carriers in the p-type semiconductor. The holes (majority charge carriers) carry most of the electric charge or electric current in the p-type semiconductor.

In p-type semiconductor, very small number of free electrons is present. Hence, free electrons are the minority charge carriers in the p-type semiconductor. The free electrons (minority charge carriers) carry only a small amount of electric current in the p-type semiconductor.

The total number of negative charge carriers (free electrons) in p-type semiconductor is less than the total number of positive charge carriers (holes) in the p-type semiconductor. 

Total negative charge carriers < Total positive charge carriers