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. Specifically, night vision devices (NVD) would greatly benefit from extremely sensitive CMOS-compatible focal plane arrays (FPAs) capable of detecting a signal in the NIR. Current intensifier tube technology in NVDs is bulky in size and weight, and does not lend itself to being fused with typical infrared sensors. There is an urgent need for a NIR FPA technology that can address the following two fundamental challenges: direct integration with Si-based CMOS readout integrated circuits (ROICs) and extreme sensitivity at low NIR light levels. Nanohmics, Inc. teaming with Dr. Jennifer A. Hollingsworth at Los Alamos National Laboratory (LANL), proposes to develop uncooled ultrasensitive CMOS-based NIR FPAs based on a graphene phototransistor architecture photosensitized with NIR-absorbing semiconductor core/shell nanocrystals (NCs). This approach combines the high IR absorption of the NC thin film with the inherent device gain of graphene gated by the transfer of photogenerated carriers. This gain leads to ultrahigh photoresponsivity and specific detectivity D*. The use of graphene and colloidal NCs allows direct monolithic integration with Si-based ROICs and will enable low-cost mass production of NIR FPAs with large format and small pitch. Nanohmics has already demonstrated a preliminary NIR device operating at room temperature, which will be further optimized in this Phase I effort. In Phase I, the team will demonstrate a proof-of-concept uncooled ultrasensitive graphene-based NIR detector. The team will synthesize core/shell NCs, fabricate, and test single graphene-NC detector elements with responses in low light conditions in the NIR. The team will also develop engineering methods to design a ROIC for Phase II and demonstrate the feasibility of direct ROIC integration. The Phase II program will advance the design and performance of the proof-of-concept to improve detector-level metrics, including quantum efficiency, D*, and frame rate. Phase II will concentrate on optimization of the prototype design and monolithic integration of an appropriate array with a commercially available ROIC to form an FPA. This type of detector can be extended into other bands, including SWIR, MWIR, and LWIR. The advantages of uncooled operation of a low-cost, low-SWaP, high-speed graphene-based IR detectors will provide a multitude of market opportunities. It will be extremely valuable for a wide variety of military and civilian applications, including intelligence, surveillance, and reconnaissance (ISR); border security ISR for the Department of Homeland Security (DHS); chemical analysis of emissions; and detection of improvised explosive devices (IEDs).