(5) (3 points) When a donor type impurity is added to a host material .what type of a semiconductor (n or p - type) is obtained? Why? Solution When we add donor type impurities to the intrinsic semiconductor, we will have a n-type semiconductor. N-type semiconductors are the semiconductors having larger electron concentration. P-type semiconductors are the semiconductors having larger hole concentration. In n-type semiconductor electrons are the majority carriers and holes are the minority carriers. The donor elements are form the Group 5 elements in the periodic table. these elements are the have 5 valence electrons. when we add these impurities, the host material like silicon forms bond with donor elements. Here the silicon has only 4 valence electrons and these electrons participate in bonding. But the donor element has 5 valence electrons. so, after the bond formation one electron is weakly bonded. at room temperature this 5th electron can freely move around the lattice and can carry currents. So, in this way we have extra electrons while adding donor atoms. As we have extra electrons, due to this electrons are the majority carriers. when electrons are the majority carriers, it is an n-type semiconductor. So, in this way adding donor type impurity makes the host material n-type semiconductor..

1. (5) (3 points) When a donor type impurity is added to a host material .what type of a
semiconductor (n or p - type) is obtained? Why?
Solution
When we add donor type impurities to the intrinsic semiconductor, we will have a n-type
semiconductor. N-type semiconductors are the semiconductors having larger electron
concentration. P-type semiconductors are the semiconductors having larger hole concentration.
In n-type semiconductor electrons are the majority carriers and holes are the minority carriers.
The donor elements are form the Group 5 elements in the periodic table. these elements are the
have 5 valence electrons. when we add these impurities, the host material like silicon forms bond
with donor elements. Here the silicon has only 4 valence electrons and these electrons participate
in bonding. But the donor element has 5 valence electrons. so, after the bond formation one
electron is weakly bonded. at room temperature this 5th electron can freely move around the
lattice and can carry currents. So, in this way we have extra electrons while adding donor atoms.
As we have extra electrons, due to this electrons are the majority carriers. when electrons are the
majority carriers, it is an n-type semiconductor. So, in this way adding donor type impurity
makes the host material n-type semiconductor.