Question

A photodiode with a bandgap energy of \(1.43\ \text{eV}\) has a cut-off wavelength approximately equal to

• A. \(870\ \text{nm}\)
• B. \(1550\ \text{nm}\)
• C. \(650\ \text{nm}\)
• D. \(1310\ \text{nm}\)

Hint:

The cut-off wavelength of a semiconductor is \[ \boxed{ \lambda_c(\text{nm})=\frac{1240}{E_g(\text{eV})} } \]

Answer 1

The Correct Option is A

Step 1: Use the cut-off wavelength formula. The cut-off wavelength is \[ \lambda_c=\frac{1240}{E_g}, \] where - \(\lambda_c\) is in nm, - \(E_g\) is in eV.

Step 2: Substitute the given value. Given, \[ E_g=1.43\ \text{eV}, \] \[ \lambda_c = \frac{1240}{1.43} \approx 867\ \text{nm} \approx 870\ \text{nm}. \] Hence, \[ \boxed{870\ \text{nm}} \] Therefore, \[ \boxed{(A)} \] is the correct answer.