Dark Current Transport and Junction Capacitance Mechanism in InP One-Side Junction Photodiodes

Photodiodes serve as pivotal components in optical data links, where minimized dark current and junction capacitance is vital for improving the detection sensitivity and response speed of the devices. This study experimentally and theoretically demonstrates that the one-side junction photodiode (OSJ-PD) exhibits reduced dark current and diminished junction capacitance. Notably, the device has a capacitance density of 2.2 \times 10^{-4}\ \mathrm {pF} / \mu \mathrm {m}^{2} and a dark current density of 2.4 \times 10^{-5}\ \mathrm {nA} / \mu \mathrm {m}^{2} at −5 V bias. Numerical simulations of current-voltage characteristics reveal that Shockley-Read-Hall (SRH) and trap-assisted tunneling (TAT) currents dominate dark current at low reverse bias from 0 V to −14 V, while band-to-band tunneling (BBT) current prevails at higher reverse bias from −14 V to −20 V. This study, for the first time, explains the trend of the variation in the dark current curve with bias voltage based on the generation mechanisms of dark current. Furthermore, we have theoretically demonstrated that the dark current of the OSJ-PD is insensitive to defect density at low voltages, and attributed the low junction capacitance to the wide depletion layer nature of the OSJ-PDs. These findings provide a comprehensive understanding of carrier transport and give a demonstration to analyze the current variation within diverse photodiodes.