Role of surface passivation in integrated sub-bandgap silicon photodetection.

We study experimentally the effect of oxide removal on the sub-bandgap photodetection in silicon waveguides at the telecom wavelength regime. Depassivating the device allows for the enhancement of the quantum efficiency by about 2-3 times. Furthermore, the propagation loss within the device is significantly reduced by the oxide removal. Measuring the device 60 days after the depassivation shows slight differences. We provide a possible explanation for these observations. Clearly, passivation and depassivation play an essential role in the design and the implementation of such sub-bandgap photodetector devices for applications such as on-chip light monitoring.

CMOS-compatible electro-optical SRAM cavity device based on negative differential resistance.

The impending collapse of Moore-like growth of computational power has spurred the development of alternative computing architectures, such as optical or electro-optical computing. However, many of the current demonstrations in literature are not compatible with the dominant complementary metal-oxide semiconductor (CMOS) technology used in large-scale manufacturing today. Here, inspired by the famous Esaki diode demonstrating negative differential resistance (NDR), we show a fully CMOS-compatible electro-optical memory device, based on a new type of NDR diode. This new diode is based on a horizontal PN junction in silicon with a unique layout providing the NDR feature, and we show how it can easily be implemented into a photonic micro-ring resonator to enable a bistable device with a fully optical readout in the telecom regime. Our result is an important stepping stone on the way to new nonlinear electro-optic and neuromorphic computing structures based on this new NDR diode.

MoSe2/WS2 heterojunction photodiode integrated with a silicon nitride waveguide for near infrared light detection with high responsivity.

We demonstrate experimentally the realization and the characterization of a chip-scale integrated photodetector for the near-infrared spectral regime based on the integration of a MoSe2/WS2 heterojunction on top of a silicon nitride waveguide. This configuration achieves high responsivity of ~1 A W-1 at the wavelength of 780 nm (indicating an internal gain mechanism) while suppressing the dark current to the level of ~50 pA, much lower as compared to a reference sample of just MoSe2 without WS2. We have measured the power spectral density of the dark current to be as low as ~1 × 10-12 A Hz-0.5, from which we extract the noise equivalent power (NEP) to be ~1 × 10-12 W Hz-0.5. To demonstrate the usefulness of the device, we use it for the characterization of the transfer function of a microring resonator that is integrated on the same chip as the photodetector. The ability to integrate local photodetectors on a chip and to operate such devices with high performance at the near-infrared regime is expected to play a critical role in future integrated devices in the field of optical communications, quantum photonics, biochemical sensing, and more.