Two-step etch in n-on-p type-II superlattices for surface leakage reduction in mid-wave infrared megapixel detectors

This work investigates the potential of p-type InAs/GaSb superlattice for the fabrication of full mid-wave megapixel detectors with n-on-p polarity. A significantly higher surface leakage is observed in deep-etched n-on-p photodiodes compared to p-on-n diodes. Shallow-etch and two-etch-step pixel geometry are demonstrated to mitigate the surface leakage on devices down to 10 mu m with n-on-p polarity. A lateral diffusion length of 16 mu m is extracted from the shallow etched pixels, which indicates that cross talk could be a major problem in small pitch arrays. Therefore, the two-etch-step process is used in the fabrication of 1280 x 1024 arrays with a 7.5 mu m pitch, and a potential operating temperature up to 100 K is demonstrated.