Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Gallium Arsenide (GaAs) is a direct-band gap semiconductor and GaP is an indirect - band gap semiconductor.
Reason (R) : In GaAs, top of valence band and bottom of conduction band are both at the same center point in Brillioun Zone, while in GaP top of the valence band is at a different position from the bottom of conduction band in Brillioun Zone.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Remember that optical emission (light generation) is highly efficient in Direct bandgap materials (GaAs, InP, GaN) because momentum is automatically conserved. Indirect materials (Si, Ge, GaP) are terrible light emitters because they require a "lucky" 3-body collision (electron, hole, and phonon).

Answer 1

The Correct Option is A