We can obtain the concentration of minority and majority carriers in
n-type and p-type materials using law of mass action.

**n-type material :**

For n-type material it is seen that, n

_{n}= N_{D}.
At any fixed temperature, according to law of mass action,

n

_{n}x p_{n}= n_{i}^{2 }
where n

_{n}is electrons i.e. majority carriers concentration while p_{n}is hole i.e. minority carriers concentration. Using n_{n }≈ N_{D}, we can write minority carrier concentration as,
N

_{D }p_{n}= n_{i}^{2 }**.**p

^{.}._{n}= n

_{i}

^{2}/N

_{D }.....................(1)

**Note**: Knowing n

_{i}and N

_{D}, the number of holes in n-type material i.e. minority carrier concentration can be obtained.

**p-type material :**

For p-type material it is seen that, p

_{p}= N_{A}.
According to law of mass action,

n

_{p}x p_{p}= n_{i}^{2 }
where n

_{p}is electrons i.e. minority carrier concentration while is holes i.e. majority carrier concentration. Using p_{p}≈ N_{A }we can write.**.**n

^{.}._{p}= n

_{i}

^{2}/N

_{A}............... (2)

**Note**: Knowing n

_{i}and N

_{A}, the number of electrons in p-type material i.e. minority carrier concentration can be obtained.

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