Ultrasensitive Near-Infrared Detector Based on Graphene-Nanocrystal Heterostructure

Ultrasensitive low light level detection and sensing in the near infrared (NIR) is critical for many military applications. Night vision devices (NVD) will greatly benefit from extremely sensitive CMOS-compatible focal plane arrays (FPAs). Current NVD intensifier technology has substantial size, weight, and power (SWaP) requirements, and does not lend itself to being fused with typical infrared (IR) sensors. There is an urgent demand for NIR FPA technology that can provide extreme sensitivity at low NIR light levels and allow direct integration withĀCMOS readout integrated circuits (ROICs). Nanohmics, Inc., teaming with Dr. Jennifer Hollingsworth at Los Alamos National Laboratory (LANL), is developing low-SWaP, uncooled ultrasensitive NIR FPAs based on a graphene phototransistor architecture photosensitized with NIR-absorbing colloidal quantum dot (QD) nanocrystals (NCs). This architecture combines the high IR absorption of the QD thin film with the inherent device gain of graphene gated by photogenerated carriers. This gain leads to ultrahigh photoresponsivity and specific detectivity D*. These FPAs should achieve performance parity with analog night vision (NV) systems, while leveraging the advantages of digital imaging, such as compatibility with data sharing, augmented reality (AR), and machine learning (ML) for targeting. The use of graphene and QDs allows direct integration with CMOS ROICs and will enable low-cost mass production of FPAs. The Phase I program successfully demonstrated the feasibility of uncooled ultrasensitive FPAs through the design, fabrication, and testing of photodetectors based on QD-sensitized graphene, operating in the spectral range 0.8-1.3ĀĄm. The team established methods for graphene transfer, QD fabrication, graphene-QD integration, and scale-up to manufacturing. Nanohmics also designed a CMOS-based FPA prototype to be fabricated and tested during the Phase II program, and identified CMOS ROIC foundry services for initial low-cost prototyping and longer-term production scale-up. During Phase II the team will fabricate a compact, uncooled, graphene-QD FPA prototype by integrating QD-sensitized graphene photodetectors with a CMOS ROIC, achieving TRLĀ4. The team will increase sensitivity, spectral range, frame rate, and device ruggedness by improving the QD sensitizer, optimizing ROIC integration, and developing an encapsulation process. Graphene-CMOS integration will be addressed early in PhaseĀII using foundry services that will provide a direct path to increasing imaging resolution and production volume while maintaining low costs ¢ accelerating technology transition and follow-on commercialization. The PhaseĀII IR FPA prototype will be delivered to the Army sponsor for testing and transition to an Army partner during Phase III. The FPA technology can be extended into other bands, including SWIR, MWIR, and LWIR, making it extremely valuable for a wide variety of military and civilian applications.