Lin Yiding, Lee Kwang Hong, Son Bongkwon, Tan Chuan Seng
Opt Express. 2021 Feb 1;29(3):2940-2952. doi: 10.1364/OE.405364.
Germanium (Ge)-based photodetectors have become one of the mainstream components in photonic-integrated circuits (PICs). Many emerging PIC applications require the photodetectors to have high detectivity and low power consumption. Herein, we demonstrate high-detectivity Ge vertical p-i-n photodiodes on an in-situ heavily arsenic (As)-doped Ge-on-Si platform. The As doping was incorporated during the initial Ge-on-Si seed layer growth. The grown film exhibits an insignificant up-diffusion of the As dopants. The design results in a ∼45× reduction on the dark current and consequently a ∼5× enhancement on the specific detectivity (D*) at low reverse bias. The improvements are mainly attributed to the improved epi-Ge crystal quality and the narrowing of the device junction depletion width. Furthermore, a significant deviation on the AsH flow finds a negligible effect on the D* enhancement. This unconventional but low-cost approach provides an alternative solution for future high-detectivity and low-power photodiodes in PICs. This method can be extended to the use of other n-type dopants (e.g., phosphorus (P) and antimony (Sb)) as well as to the design of other types of photodiodes (e.g., waveguide-integrated).
锗（Ge）基光电探测器已成为光子集成电路（PIC）中的主流组件之一。许多新兴的PIC应用要求光电探测器具有高探测率和低功耗。在此，我们展示了在原位重掺砷（As）的硅基锗平台上的高探测率锗垂直p-i-n光电二极管。在初始的硅基锗籽晶层生长过程中掺入了砷掺杂。生长的薄膜显示出砷掺杂剂的向上扩散不明显。该设计使暗电流降低了约45倍，从而在低反向偏压下使比探测率（D*）提高了约5倍。这些改进主要归因于外延锗晶体质量的提高和器件结耗尽宽度的变窄。此外，砷化氢流量的显著偏差对D*增强的影响可忽略不计。这种非常规但低成本的方法为未来PIC中的高探测率和低功耗光电二极管提供了一种替代解决方案。该方法可以扩展到使用其他n型掺杂剂（例如磷（P）和锑（Sb））以及设计其他类型的光电二极管（例如波导集成型）。
