Intrinsic Layer Zn Doping Diffusion Control and Bandwidth Modulation of InP/InGaAs/InP Photodiode

In the InP/InGaAs/InP PIN photodetector material growth, zinc is a normal doping ion and it has a high diffusion coefficient in InP and InGaAs. The Zn diffusion depth at the p-InP and intrinsic InGaAs boundary is critical for PIN photodiode high frequency characteristics. We control the p-InP Zn doping diffusion into intrinsic InGaAs layer by reducing the growth temperature of the p-type InP, decreasing the Zn doping concentration of the InGaAs/InP boundary, and increasing the growth rate of p-InP. We derive the exact voltage-controlled PIN photodiode capacitance expressions as a function of the Zn diffusion depth in the InGaAs intrinsic layer. This work reveals that the RC bandwidth of p-doping diffusion photodiode capacitance can be controlled by reverse voltage. And it gives a novel reference to design photodiode and varactor in optical microwave mixed circuits.