Cavity-enhanced Multispectral Photodetector on a Si Platform: Theory, Materials, and Devices

Abstract

We report the design and fabrication of a novel multispectral photodetector capable of detecting multiple wavebands in a single pixel. Our prototypical device demonstrates spectral selectivity with a peak responsivity of 65.4V/W at 3.9μm wavelength. 2010 Optical Society of America OCIS codes: (110.4234) Multispectral and hyperspectral imaging; (040.5160) Photodetectors. IntroductionMultispectral infrared (IR) detection has been widely employed for numerous applications including hyperspectral imaging, IR spectroscopy, and target identification. Traditional multispectral detection technology is based on the combination of single spectral Focal Plane Arrays (FPAs) and spectral filters, grating spectrometers, or Fourier transform spectrometers, all of which require bulky, high-cost mechanical scanning instruments and have a slow response. Single pixels capable of detecting multiple wavebands simultaneously, however, enable dramatically simplified system design with superior mechanical robustness. The development of third generation IR detector and FPA featuring multispectral detection capability in a single pixel is thus garnering a lot of interest around the world today [1]. Recently, three-color photodiodes based on HgCdTe have been demonstrated, although their spectral cross talk is still large (> 10%) due to radiative coupling [2]. Another competing multi-color detector technology is quantum-well IR photodetectors (QWIPs) based on standard III-V semiconductors [1]. However, further QWIP device optimization is largely limited by its low quantum efficiency (< 10%) [3]. A solution which combines high quantum efficiency and low spectral cross talk is highly desirable yet remains to be explored.Our work builds on the concept of phase-tuned propagation of resonant modes in cascaded planar cavities for multispectral detection, and the use of polycrystalline films for monolithic integration on Si. In this paper, we present a systematic study starting with the theory and design methodology of a novel multispectral cavity-enhanced photodetector using phase-tuned propagation; we then describe the demonstration of highly IR-sensitive polycrystalline PbTe films free of high-temperature sensitization, a prerequisite for integration with Si read-out integrated circuitry (ROIC), and conclude with fabrication and testing of a mid-IR spectral selective photodetector.