Modeling the dynamic capacitance of an LED in forward bias

To design effective circuits that modulate the optical output of LEDs in communication systems, it is essential to accurately model their electrical response, particularly to small modulation signals. The dynamic resistance of an LED is known to depend on the DC bias and can be obtained from the Shockley diode equation. However, the modeling of its dynamic capacitance has been much less explored. This paper proposes a novel approach to modeling the dynamic capacitance of an LED under forward bias. By combining the Shockley equation with the ABC electron–hole recombination rates in a novel way, we derive an analytical expression. We verify the accuracy of our model using experimental data in the 1–100 MHz range, which corresponds to the modulation bandwidth defined in the ITU G.vlc standard for LiFi.