Mid-wavelength infrared focal plane array based on type II InAs/GaSb superlattices on InP substrate

We report the growth and characterization of band gap engineered mid-wavelength infrared photodiode, pBiBn, based on type-II InAs/GaSb superlattices on InP substrate. InP substrates are attractive material because they have high transmittance in the mid-wavelength infrared region and near thermal expansion coefficient to Si read-out IC (ROIC). Misfit dislocations due to lattice mismatch between GaSb and InP were successfully suppressed by thick GaSb buffer layer and two step growth of it. The photoluminescence (PL) spectrum from the absorption layers exhibits a peak wavelength of 5.01 μm at 77 K. The distinct PL peak was observed even at 120 K, indicating the excellent crystalline quality of T2SLs grown on an InP substrate. The dark current densities of 292 × 10−6 A/cm2 at 77 K and cut off wavelength of 5.15 μm at 80 K were measured, respectively. A clear image was obtained by fabricated focal plane array of 640 × 512 pixels with 15 μm pixel pitch, and NEDT and defective pixel rate was 50 mK and less than 1 % at 100 K, respectively.