Model for speed performance of quantum-dot waveguide photodiode

A model is proposed that makes it possible to analytically analyze the speed performance of a waveguide $p$–$i$–$n$ photodiode with a light-absorbing region representing a multilayered array of quantum dots separated by undoped spacers. It is shown that there is an optimal number of layers of quantum dots, as well as an optimal thickness of the spacers, which provide the widest bandwidth. The possibility of achieving a frequency range (at the level of -3 dB) above 20 GHz for waveguide photodiodes based on InGaAs/GaAs quantum well-dots is shown.