Hydrodynamic Simulations of Unitraveling-Carrier Photodiodes

Journal article, 2007

We present simulated results of a unitraveling-carrier photodiode (UTC-PD) using the hydrodynamic carrier transportation model. A maximum responsivity of 0.25 A/W and a small-signal 3-dB bandwidth of 52 GHz were obtained for a 220-nm-thick InGaAs absorption layer. The physical properties of the UTC-PD have been investigated at different optical injection levels. Modulation of the energy-band profile due to the space charge effect has been observed at high injection level, and an electron velocity overshoot of 3e7 cm/s has been found to effectively delay the onset of space charge effects. Comparisons with reported simulated results using the drift–diffusion model as well as reported experimental results are presented. The results suggest the necessity of using the hydrodynamic transport equations to accurately model the UTC-PD. In addition, it has been corroborated that the photoresponse of the UTC-PD could be improved by incorporating a graded doping profile in the absorption layer.