CAREER: Avalanche Confinement in Single-Photon Avalanche Diodes: A Novel Paradigm for Imaging near the Quantum Limit

Solid-state single-photon detectors are a class of light sensors that are designed to detect and process light at single photon resolution. These sensors enable a wide variety of modern technologies like quantum computing and integrated biosensor platforms for biomedical analysis. One novel technology trend is to integrate single-photon sensors with microelectronic chips.

This integration provides on-board signal processing in addition to ready interfacing with other systems. While there has been much progress in the development of integrated single-photon sensors, there remain quite a few scientific and technological barriers to their widespread adoption. For example, the tradeoffs between noise, temperature, resolution, and photodetection efficiency remain unfavorable for many applications.

The proposed research takes a layered approach toward solving some of these outstanding issues, in addition to uncovering new applications in which integrated single photon sensors can provide added benefit or entirely new capabilities. Furthermore, a broader impact of the proposed research program will be a framework that features early educational experiences in optoelectronic science and engineering for middle and high school students.

The framework will also include a robust translational research component and an entrepreneurship practicum for both undergraduate and graduate students.

The project will feature the development of single-photon avalanche diodes (SPADs) in which the spatiotemporal profile of avalanche currents may be tailored dynamically. This feature, called avalanche confinement, represents a stark departure from current approaches in the development of SPADs; it will yield improved signal-to-noise ratio at room temperature without compromising photon detection efficiency and resolution.

The project will be structured in three independent and synergistic research tasks. The first task will focus on establishing a scientific framework that explains avalanche confinement. This will include the development of calibrated device-physics models that leverage quantum kinetic equations to describe the carrier transport processes at play during avalanche confinement.

These device-physics models will be used to augment electronic circuit models that can be used in high-level system designs. The first task will include the development of both silicon and silicon carbide SPADs. Under the second task, silicon SPADs will be integrated in standard, i.e., non-specialized, complementary metal-oxide semiconductor (CMOS) microchip technologies to demonstrate a new class of imagers in which pixels operate under avalanche confinement.

This integration will enable single photon imagers that can detect light near the quantum limit and at room temperature, i.e., without cooling. Imagers developed under the second task will be evaluated in passive imaging and in fluorescence lifetime imaging for in-incubator biological cell culture analysis. Lastly, under the third task, applications of avalanche-confined SPADs to true random number generation and physically unclonable functions for hardware security will be explored.

Together, work under these three tasks will advance the field by establishing a transformative paradigm for the design of single-photon detection and imaging.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.