Gain Feedbacked Thermal Heterostructure Transistor for Long Wavelength IR 8 to 12 micrometer Detection: Breaking the fundamental limit of bolometric TCR
Abstract
Our team proposes a three-year program to investigate and develop a novel transistor bolometer that leverages a distinctive gain feedback mechanism to achieve an ultrahigh temperature coefficient of resistance (TCR) for uncooled high-speed, high-sensitivity LWIR sensing and imaging. Uncooled bolometers have been widely utilized in this spectral range due to their compact nature, although their performance lags behind their cooled counterpart, such as mercury cadmium telluride (MCT) photodetectors. One key factor that limits the sensitivity and speed of existing bolometers is the low TCR, which is primarily constrained by the activation energy of the bolometer material.Addressing this limit, we propose to break the fundamental limit of bolometric TCR with novel thermal transistors in this program. The thermal transistor features a unique gain feedback mechanism, which our team recently rediscovered in heterostructure transistors. The preliminary experimental results and theoretical analysis indicate that TCR in the proposed thermal transistor can be well above 40%/Kelvin, and in principle, there is no upper limit. Such a high TCR will allow for the realization of high-speed operation well beyond kHz with high sensitivity.In this program, our team will implement a three-step plan, aiming to demonstrate the gain feedbacked thermal transistor with NETD of 25 mK and speed of 100 kHz. First, we will design the epitaxial structures ofthermal transistors, characterize their temperature-dependent properties, and reveal the intrinsic TCR limits and sharpness of transition edge mode. In this step, we will focus on fundamental device physics and elucidate the contributions of different factors (such as band offset, doping, layer thickness, and the nature of the bandgap) in determining the temperature dependence of thermal transistors. Second, we will design and characterize two types of meta-structures to achieve broadband, >90% LWIR absorption with minimized heat capacity. Finally, we will integrate the LWIR meta-structure absorber with the optimized and suspended thermal transistor to demonstrate the LWIR sensing with high sensitivity and speed (we name the fully integrated device a "transistor bolometer"). Moreover, we will also lay out the pathways for manufacturing focal plane arrays based on such transistor bolometers.The uncooled mid-infrared sensors and imagers in the LWIR band are of critical importance to Navy s missions. This technology will enable soldiers and weapon systems to see, detect, and communicate clearer, further, and faster using the uncooled transistor bolometers with significantadvantages in size, weight, and power consumption (SWaP). The uncooled, ultrafast transistor bolometers developed by our team will also enable numerous applications important to DoD, including fast night vision, precise guidance systems, future LiDAR in LWIR, free-space optical communications, and much more.Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 15, 2024
- Source ID
- N000142412307
Entities
People
- Fengnian Xia
Organizations
- Office of Naval Research
- United States Navy
- Yale University