Development status of Type II superlattice infrared detector in JAXA

We present the development status of Type II superlattice (T2SL) infrared detector in JAXA. Since 2009, we have started a basic research on InAs/GaSb T2SL infrared detectors. Our final goal is to realize the T2SL array detector having a cutoff wave length of λc=15 μm. In order to confirm a technical feasibility of 15 μm cutoff T2SL detector, we fabricated T2SL samples having a different thickness of InAs/ 7 monolayers (ML) GaSb. These crystals are designed for the cutoff wavelength from 6 μm to 15 μm. The X-ray Diffraction measurement shows a mismatch between the substrate and superlattice layers is below 0.006%. The surface morphology of the samples with an atomic force microscope is 1.5-3.3 Å RMS for 5×5 μm square regions. We also fabricated single pixel detectors with these crystals. We show the results of the spectral response measurement using a FTIR system. We also show the development status of an array detector. The array detector having the cutoff wavelength of 6 μm is successfully demonstrated. However, further improvements are required for a future 15 μm cutoff array detector.