(Invited) Advances in Wide Bandgap Thermal Resonant Infrared Detectors
Authors: Rais-Zadeh Mina 
Published: August 2024

Exploring the surface of distant planets, notably Venus, requires robust technologies capable of withstanding extreme environmental conditions while providing valuable scientific insights. This paper delves into the advancements made in designing an instrument tailored for capturing infrared (IR) images in the harsh Venusian environment, where temperatures soar to 500°C. The presented IR detector harnesses the power of a sparse array of resonant-based micromechanical devices, strategically addressing the limitations of existing technologies that can only withstand extreme conditions for limited durations.

At the core of this technology lies the utilization of high-temperature-tolerant InAlN/GaN as the primary resonating element. GaN's resilience and high temperature tolerance make it a crucial player in challenging space environments. Its wide bandgap and chemical stability are advantageous for enduring harsh conditions during space missions. In tandem with GaN's intrinsic properties, high-temperature-tolerant meta-absorbers strategically positioned on the surface of each pixel play a pivotal role in the functionality of the IR detector. These meta-absorbers exhibit a remarkable capacity to absorb incoming infrared (IR) radiation, promptly transforming it into heat. The resonant frequency of these devices exhibits a linear shift with temperature variations, and a high-temperature-tolerant read-out electronic adeptly senses this frequency shift, enabling the seamless transfer of imaging data. Extraction of IR source power occurs through the resonance frequency shift in the exposed GaN resonator, compared to a reference resonator. The reference resonator, lacking the IR-absorbing layer, establishes a baseline for minimal resonant shifts.

The sparse array configuration strategically reduces imaging elements to optimize power consumption and cost-effectiveness. Inspired by techniques employed in medical imaging instruments, this approach allows the construction of images from a low-power 2D array, striking a balance between imaging capabilities and processing efficiency. This sparse array configuration serves a dual purpose, streamlining signal routing for integrated read-out electronics and simplifying the overall integration and packaging of the IR imaging instrument. Monolithic integration of the read-out electronic with the sensor platform on the same chip overcomes challenges related to electrical and mechanical stability at high temperatures.

The resonant effect delivers a remarkable enhancement in the signal-to-noise ratio, surpassing existing thermal detector technologies by a factor of 70×. Furthermore, the strategic implementation of sparse arraying results in approximately a 4× reduction in power consumption, presenting an efficient and resilient solution for imaging in extreme environments. Diverging from traditional IR detectors limited in performance at high temperatures, these detectors rely on the temperature coefficient of elasticity (TCE), offering a wide dynamic range of operational temperatures.

Finally, this paper includes recent results measured at 500°C, demonstrating the instrument's capability to operate effectively in Venus's challenging conditions. These advancements pave the way for future planetary exploration missions, promising a deeper understanding of Venus's geological and atmospheric processes.