Thin Film AlN Microbolometer for Very Long-Wave Infrared Detection

TL;DR

This paper presents a suspended thin-film AlN microbolometer capable of narrowband very long-wave infrared detection, with enhanced absorption and spectral response tailored to 14-18 um wavelengths.

Contribution

The work introduces a novel AlN microbolometer design with a perforation pattern for improved absorption and thermal performance in the VLWIR range.

Findings

Peak responsivity of 920.8 ppm/mW at 15.48 um

Narrowband spectral response observed in 14-18 um range

Resonant absorption enhanced by suspension and patterning

Abstract

We demonstrate a suspended thin-film aluminum nitride (AlN) microbolometer for narrowband very long-wave infrared detection. The device uses a 100-nm-thick AlN membrane suspended above a Pt back reflector by a 1-um air gap. Resonant absorption is set by the AlN transverse optical phonon near 15.4 um and is strengthened by suspension above the reflector. A periodic perforation pattern reduces membrane thermal mass and enhances absorption without further thinning the film. DC resistance measurements under tunable infrared illumination verify bolometric operation, and the measured spectral response follows the absorption profile expected from spectroscopic measurement of passive devices. Narrowband response is observed in the 14--18 um range, with peak responsivity of 920.8 ppm/mW at 15.48 um. This platform can enable compact wavelength-selective thermal detectors for multispectral imaging, on-chip infrared spectroscopy, and chemical sensing.