Current-Assistance (CA) has emerged as a popular pathway for high-performance time-resolved imaging in the near-infrared spectrum. It demodulates photogenerated charges classically by injecting Ohmic majority currents in a low-resistivity epilayer, obtaining a uniform drift field deep into the photodetection volume. To reduce its power consumption, recent implementations utilize high-resistivity epilayers, which introduce strong nonlinearities in the resulting drift fields. This work provides a physical description of the distribution of drift fields in high resistivity silicon substrates by considering that the injected majority currents are in fact Space-Charge-Limited (SCL). A two-dimensional analytical model for the potential and electric field in the epilayer is derived and validated using TCAD drift-diffusion simulations, introducing the concept of the Virtual Cathode (VC) for CA. The SCL nature of the injected majority current is verified through I-V measurements. These insights establish a physical understanding for the design of future current-assisted photodetectors in high-resistivity epilayers.
Vrijsen, JEJ, Nevens, W, Kuijk, M, Ingelberts, H & Van Den Dries, T 2026, 'Space-Charge-Induced Drift Fields in High-Resistivity Silicon Substrates for Current-Assisted Photodetectors', IEEE Electron Device Letters. https://doi.org/10.1109/LED.2026.3695145
Vrijsen, J. E. J., Nevens, W., Kuijk, M., Ingelberts, H., & Van Den Dries, T. (2026). Space-Charge-Induced Drift Fields in High-Resistivity Silicon Substrates for Current-Assisted Photodetectors. IEEE Electron Device Letters. https://doi.org/10.1109/LED.2026.3695145
@article{2c1d7e187a7a4a398b4054c28aa4b22f,
title = "Space-Charge-Induced Drift Fields in High-Resistivity Silicon Substrates for Current-Assisted Photodetectors",
abstract = "Current-Assistance (CA) has emerged as a popular pathway for high-performance time-resolved imaging in the near-infrared spectrum. It demodulates photogenerated charges classically by injecting Ohmic majority currents in a low-resistivity epilayer, obtaining a uniform drift field deep into the photodetection volume. To reduce its power consumption, recent implementations utilize high-resistivity epilayers, which introduce strong nonlinearities in the resulting drift fields. This work provides a physical description of the distribution of drift fields in high resistivity silicon substrates by considering that the injected majority currents are in fact Space-Charge-Limited (SCL). A two-dimensional analytical model for the potential and electric field in the epilayer is derived and validated using TCAD drift-diffusion simulations, introducing the concept of the Virtual Cathode (VC) for CA. The SCL nature of the injected majority current is verified through I-V measurements. These insights establish a physical understanding for the design of future current-assisted photodetectors in high-resistivity epilayers.",
keywords = "near-infrared (NIR), Current-Assistance, space charge limited current, high-resistivity silicon",
author = "Vrijsen, \{Jonathan Ernest J\} and Wannes Nevens and Maarten Kuijk and Hans Ingelberts and \{Van Den Dries\}, Thomas",
year = "2026",
month = may,
day = "20",
doi = "10.1109/LED.2026.3695145",
language = "English",
journal = "IEEE Electron Device Letters",
issn = "0741-3106",
publisher = "IEEE",
}