High-performance uni-traveling-carrier photodiodes with a new collector design

We report two uni-traveling-carrier photodiode (PD) structures, for high-power and high-linearity applications. Using a thick collection layer (500 nm), the fabricated 25-mu m-diameter PDs achieve a -3-dB bandwidth up to 29 GHz, and a maximum dissipated heat power of about 480 mW, simultaneously. A new collector design with a nonuniform doping profile is proposed to better relax the space charge effect. Its performances are compared to a uniformly doped collector layer. Saturation currents and third-order intermodulation distortion measurements at 20 GHz confirm the advantage of the new collector design for high-power and high-linearity performances: -1-dB saturation current as high as 120 mA and a third-order intercept point in excess of 35 dBm at 70 mA are recorded.