Development of type II superlattice detector for future space applications in JAXA

Space-borne infrared detectors require higher sensitivity, higher resolution, and larger formats than ground-based infrared detectors. In order to meet more demanding mission requirements, JAXA decided to position infrared detector technology as a strategic technology and promote its development. InAs/GaSb type II superlattices (T2SL) are the only known infrared material with a performance theoretically predicted to be higher than that of HgCdTe. If the T2SL detector is realized, it can be applied to high-sensitivity infrared sensors, which are required for many advanced instruments such as an imaging Fourier transform spectrometer. The final goal of developing the T2SL detector is to realize an array detector with a cutoff wavelength λc of 15 μm. We have started basic research on the T2SL detector. In this paper, we report on the first results for the development of T2SL detectors for the mid-wave infrared regime. The detector structure is a pin photodiode with a superlattice consisting of 9 InAs monolayers (MLs) and 7 GaSb MLs. We present the results of optical evaluation of the detector. The cutoff wavelength is 5.5 μm at 30 K. The responsivity is 0.33 ± 0.05A/W at 4.5 μm.