Passivation of InSb infrared photodetectors
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Infrared detectors have wide range applications in both military and civilian life. One of the most commonly used infrared detectors is InSb detectors. InSb detector technology has been developing since 1950s. Fabricating p-n diodes to detect infrared radiation is a common way of constructing InSb detectors. Due to high free carrier concentration at room temperature, InSb detectors need to be cooled down to operate properly and usually liquid nitrogen is preferred for cooling. However, even at 77 K, tunneling and generation-recombination and surface leakage are not negligible and these effects result in dark current. Improving the photo current-to-dark current ratio is the main goal in design and fabrication of InSb photo detectors. One way of decreasing the dark current is passivating the exposed edges of the detector to reduce surface leakage current. Passivating the edges can result in decreasing in the surface leakage by eliminating the surface states (dangling bonds). Dielectric thin films like SiO2 and SiNx are commonly used for passivation. In this work, different sized detectors are fabricated and characterized by measuring I-V curves and spectral response. Different approaches are tested for passivation and a detailed comparison between detectors with different treatments is presented.