Growth and fabrication of a mid-wavelength infrared focal plane array based on type-II InAs/GaSbsuperlattices

Abstract

We present the fabrication of a mid-wavelength infrared focal plane array (FPA) based on type-II InAs/GaSb strain layer superlattices (SLs). The detectors contain a 400-period 8 ML InAs/8 ML GaSb SL active layer, which is grown by solid source molecular beam epitaxy on GaSb (100) N type substrates. Lattice mismatch between the superlattices and GaSb substrate achieves 148.9 ppm. The full width at half maximum of the first order satellite peak from X-ray diffraction was 28 arcsec. Single element detectors and FPA with a 128 × 128 pixels were fabricated using citric acid based solution wet chemical etching. Chemical and physical passivation effectively reduces the surface leakage and this process was characterized by I—V measurement. The devices showed a 50% cut-off wavelength of 4.73 μm at 77 K. The photodiode exhibited an R0A of 103 Ω · cm2. The FPA was characterized with an integration time of 0.5 ms and F/2.0 optics at 77 K and the average blackbody detectivity of the detectors is 2.01 × 109 cm · Hz1/2/W.