14.11 A p-n photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 6000 nm?
Step 1: Find the energy of signal.
As E=hcλ=6.626×10−34×3×1086000×10−9=3.313×10−20 J
Step 2: Find the energy of signal in electron-volt.
E=3.313×10−201.6×10−19=0.207 eV
The energy of a signal of wavelength 6000 nm is 0.207 eV, which is less than 2.8 eV (the energy band gap of a photodiode.) Hence, the photodiode cannot detect the signal.
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