A p-n photodiode is made of a material with a band gap of $2.0 ext{ eV}$. The minimum frequency of the radiat

Question

A p-n photodiode is made of a material with a band gap of $2.0	ext{ eV}$. The minimum frequency of the radiation that can be absorbed by the material is nearly:

Accepted Answer

1. **Condition for Absorption:** For a photodiode to absorb radiation, the energy of the incident photon ($E$) must be greater than or equal to the band gap energy ($E_g$) of the material. Therefore, the minimum energy required is $E = E_g$.
2. **Identify Given Data:** 
   * Band gap energy, $E_g = 2.0	ext{ eV}$
   * Convert eV to Joules: $E_g = 2.0 	imes 1.6 	imes 10^{-19}	ext{ J} = 3.2 	imes 10^{-19}	ext{ J}$
   * Planck's constant, $h \approx 6.63 	imes 10^{-34}	ext{ J s}$
3. **Calculate Minimum Frequency ($
u$):**
   * Since $E = h
u$, the minimum frequency is $
u = \frac{E_g}{h}$
   * $
u = \frac{3.2 	imes 10^{-19}	ext{ J}}{6.63 	imes 10^{-34}	ext{ J s}} \approx 0.482 	imes 10^{15}	ext{ Hz} = 4.82 	imes 10^{14}	ext{ Hz}$
4. **Conclusion:** The calculated frequency $4.82 	imes 10^{14}	ext{ Hz}$ is closest to $5 	imes 10^{14}	ext{ Hz}$.

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