Comparison of Type I and Type II Heterojunction Unitravelling Carrier Photodiodes for Terahertz Generation

To assess the potential for terahertz generation, we have numerically simulated unitravelling carrier photodiodes with type I InGaAs/InP and type II GaAsSb-InP heterojunctions. The simulations give good agreement with published experimental results detailing device operation and 3 dB bandwidth. The optimization of these structures as photomixers by reducing the layer thickness of the absorber and varying the doping of the absorber and collector layers shows excellent potential for terahertz generation.