Final answer:
In an n-type semiconductor, the majority carriers are free electrons and the minority carriers are holes, while in a p-type semiconductor, the majority carriers are holes and the minority carriers are electrons. These carriers are critical for semiconductor functionality in electronic devices.
Step-by-step explanation:
For a) n-type semiconductor: The majority carrier is the free electron which is contributed by impurity atoms such as phosphorus or arsenic. On the other hand, the minority carrier in an n-type semiconductor is a hole produced by thermal excitations across the energy gap from the valence to the conduction band.
For b) p-type semiconductor: The majority carrier is the hole, which is contributed by impurity atoms such as boron or gallium that have one fewer valence electron than the semiconductor atoms. The minority carrier is an electron that has been thermally excited from the valence band to the conduction band.
The presence of impurity atoms increases the conductivity of semiconductors by providing additional charge carriers: electrons in an n-type and holes in a p-type. This concept is instrumental in the functionality of electronic components like diodes and transistors.