Speed performance comparison of InP/InGaAs UTC photodiodes utilizing compositionally graded and exponentially doped photo-absorption layers

The photocurrent responses of InP/InGaAs uni-traveling-carrier photodiodes having conventional, compositionally graded, and exponentially doped photo-absorption layer were investigated with photo-absorption layer doping concentrations and current densities as parameters. The speed performance of these photodiodes was calculated including the effects of conduction band potential difference associated with the hole current, the p-type doping concentration, and the built-in electric field in the photo-absorption layer. According to the simulation results, the compositionally graded and the exponentially doped UTC-PDs had a superior speed performance compared with that of the conventional one regardless of the current density and the doping concentration in the photo-absorption layer.