Strained Layer Superlattice Dual Band Mid-Wavelength Infrared/Long Wavelength Infrared (MWIR/LWIR) Focal Plane Arrays

Spire Semiconductor proposes to make InAs/GaSb based MWIR/LWIR dual-band FPA photodetectors with low surface-leakage current using the unique processing and passivation techniques developed at Spire Semiconductor. In phase I, Spire Semiconductor will demonstrate FPA pixel-sized (~30x30um-2) dual-band (5 um cutoff for MWIR and 10 um cutoff for LWIR) photodetectors and small array (320x256) with 77K dynamic Resistance-Area product RA values > 100Kohm cm-2 for MWIR and > 1Kohmcm-2 for LWIR, to satisfy the requirement for the MDA developed ROIC. Performance of the dual-band InAs/GaSb based FPAs is mainly limited by the high dark current from the LWIR diodes, and the dark current is mainly due to mesa edge leakage. The dark current problem becomes prominent as the size of the detector becomes small. This is especially true in case of high-definition LWIR FPAs, with very small bandgap materials, in which a small change in Fermi level, due to the formation of defects on the mesa sidewalls, cause an inversion of majority carriers along the sidewalls creating leakage paths. Therefore, improving the passivation techniques is of particular importance to the performance of dual-band FPAs, and this is Spire Semiconductor’s focus in this proposal.