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.