Photodiode Cutoff Wavelength Formula and Calculator

The cutoff wavelength is a key parameter that defines the spectral response limit of a photodiode. This guide explains the formula for calculating cutoff wavelength and provides a convenient calculator for accurate results.

Definition

To build up leakage current in the photodiode, the energy of the photon must be greater than or equal to the energy band gap between the valance and conduction band, called the band gap (E_g).

• h*v >= E_g

h*c/λ >= E_g

or

λ <= h*c/E_g

So, the threshold for conduction or detection is commonly called the long wavelength cutoff point (λ_c).

λ_c = h*c/E_g

Photodiode Responsivity Calculator and Example

Here’s an example using the photodiode responsivity calculator:

INPUTS:

• Eg = 1.42 eV

OUTPUTS:

• λ = 873.23 nm

Photodiode Cutoff Wavelength Formula

The following formula is used in this photodiode cutoff wavelength calculator:

Image Alt: Photodiode Cutoff Wavelength Equation, formula

Conclusion

Understanding the cutoff wavelength is vital for selecting and designing photodiodes for specific applications. Use the formula and calculator provided to ensure precise spectral response analysis.