Towards fabrication of mid-IR FPAs with enhanced sensitivity and reduced dark current by using integration with microspherical arrays

It was demonstrated previously that the efficiency of light collection by individual pixels of mid-wave infrared (MWIR) focal plane arrays (FPAs) can be enhanced by using dielectric microspheres, which provide concentration of light with large angle-of-view. This approach allows miniaturizing photodetector mesas to reduce their thermal current that, in turn, helps increasing the operating temperature of FPAs. In this work, we develop a technology of parallel integration of thousands of microspheres with the pixels. We fabricated microhole arrays and used them as suction grippers for microspheres. It is shown that in large-scale arrays formed by microspheres with several tenths microns in diameter, the fabrication errors below ~1% can be obtained. The fabrication errors can be significantly reduced in arrays formed by larger (>100 microns) microspheres.