InAs/GaInSb superlattices as a promising material system for third generation infrared detectors

Abstract

Hitherto, two families of multielement detectors have been used for infrared applications: scanning systems (first generation) and staring systems (second generation). Third generation systems are being developed nowadays. In the common understanding, third generation IR systems provide enhanced capabilities like larger number of pixels, higher frame rates, better thermal resolution as well as multicolour functionality and other on-chip functions. In the class of third generation infrared photon detectors, two main competitors, HgCdTe photodiodes and AlGaAs/GaAs quantum well infrared photoconductors (QWIPs) are considered. However, in the long wavelength infrared (LWIR) region, the HgCdTe material fail to give the requirements of large format two-dimensional (2-D) arrays due to metallurgical problems of the epitaxial layers such as uniformity and number of defective elements. A superlattice based InAs/GaInSb system grown on GaSb substrate seems to be an attractive alternative to HgCdTe with good spatial uniformity and an ability to span cut-off wavelength from 3 to 25 μm. The recently published results have indicated that high performance middle wavelength infrared (MWIR) InAs/GaInSb superlattice focal plane arrays can be fabricated. Also LWIR photodiodes with the R 0 A values exceeding 100 Ωcm 2 even with a cut-off wavelength of 14 μm can be achieved. Based on these very promising results it is obvious now that the antimonide superlattice technology is competing with HgCdTe dual colour technology with the potential advantage of standard III–V technology to be more competitive in costs and as a consequence series production pricing.