Germanium nanowire microbolometer.

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Near-infrared (IR) detection is crucial for non-destructive, non-contact inspections across various fields.
• Current bolometer-type IR sensors are limited by their micrometer-scale architectures, hindering miniaturization for advanced integrated systems.
• There is a need for scalable, CMOS-compatible IR detector technologies.

Purpose of the Study:

• To investigate the feasibility of using germanium (Ge) nanowires as the thermal sensitive element in a highly scalable, CMOS-compatible bolometer-type infrared detector.
• To characterize the performance of a Ge nanowire-based near-IR sensor.
• To optimize the detector's responsivity and temporal response for improved performance.

Main Methods:

• First-principle study and experimental characterization of Ge nanowires integrated onto a low thermal conductivity membrane.
• Implementation of a freestanding membrane with a platinum absorber for wavelength-independent near to mid-IR absorption.
• Electrical characterization, heat transport simulations (COMSOL), and lock-in measurements for performance benchmarking.

Main Results:

• Demonstrated a strong temperature dependence of resistance in Ge nanowires, with a maximum temperature coefficient of resistance of -0.07 K⁻¹ at 100 K.
• Achieved good agreement between simulated and experimental responsivity and temporal response.
• Benchmarked room-temperature detectivity and noise equivalent power, showing effective improvement by operating with parallel nanowire networks.

Conclusions:

• Germanium nanowires are a viable material for scalable, CMOS-compatible bolometer-type infrared detectors.
• The developed detector architecture shows promising performance for near-IR sensing applications.
• Operating the bolometer with parallel nanowire networks can significantly enhance detectivity and reduce noise equivalent power.