Development of Phonon-Assisted Microbolometers using Semiconductor Tunneling Junctions
Abstract
(Approved for Public Release)Microbolometers have become the technology of choice for uncooled imaging in the long-wave infrared (LWIR) band. The performance of uncooled microbolometers is limited by several noise sources, including 1/f noise and Johnson noise, which can be suppressed by enhancing the sensitivity of the bolometer temperature sensing element. We propose to develop an uncooled bolometer that incorporates an extremely sensitive temperature sensor # called the Tunneling-Diffusion Edge Sensor (TDES) # which relies on the abrupt transition of interband tunneling current to diffusion current in a tunnel diode. Our TDES method, using germanium tunnel diodes, has achieved an enhancement greater than 100-fold in temperature sensitivity over state-of-the-art vanadium oxide. The primary materials we are considering for thin-film tunnel diode TDES are germanium and silicon. Using common bolometer pixel geometries and operating parameters, our projected total noise equivalent temperature difference (NETD) for a single-pixel germanium TDES microbolometer is 10.5 mK at a bandwidth of 100 kHz, including 1/f, Johnson, readout, and thermal fluctuation noise sources.In addition to enhancing normal (thermal) detection in microbolometers, as the second goal of this project, we will explore tunnel diodesas a platform for phonon-assisted detection. Specifically, we will computationally and experimentally study device architectures tocreate tunneling junctions with strong optical phonon-assisted indirect interband tunneling characteristics. Such devices will benefit from the non-equilibrium occupation of optical phonons generated during the light absorption process and can detect incident radiation without the need for a change in the bulk temperature of the bolometer. The proposed phonon-assisted bolometry using tunneling diodes will be characterized by generating a large population of optical phonons using high-frequency pump pulses from MWIR or LWIR lasers and measuring the change in tunnel diode current via lock-in detection. Since there is no need for a bulk temperature change in the bolometer, the proposed phonon-assisted tunneling method will not be limited by thermal fluctuation noise and the thermal time constant of the bolometer, potentially allowing operation at lower NETD and significantly higher bandwidth.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2024
- Source ID
- N000142412311
Entities
People
- Amin Reihani
Organizations
- Office of Naval Research
- Rutgers University
- United States Navy