Fabrication and Characterization of SWIR/eSWIR Dual-Band nBn InGaAs Focal Plane Arrays

Gül, Musa Selim
In the scope of this thesis study, an InGaAs based nBn-type photodetector with dual-band capability is grown with a molecular beam epitaxy system. To compensate the valence band offset, a delta doping layer is used in the compositionally graded InAlGaAs barrier region. A focal plane array is fabricated and characterized with the grown photodetector material. Optical measurement results show peak quantum efficiency for extended short wavelength infrared (eSWIR) operating mode as %60 at 1.7 μm and the cut-off wavelength of the detector for eSWIR mode is 2.0 μm. For SWIR operation mode, %48 peak quantum efficiency is obtained at 1.5 μm and the cut-off wavelength for SWIR mode is 1.7 μm. These results are obtained without anti-reflection coating for eSWIR and SWIR modes and there exists low-level optical crosstalk between modes. These high quantum efficiency values indicate valence band offset has been successfully moved to the conduction band by applying the delta doping technique. Dark current densities are obtained as 3 mA/cm^2 at room temperature and 0.4 μA/cm^2 at 200 K for eSWIR mode. SWIR mode operation can be accomplished with %43 peak quantum efficiency without applying biasing voltage. Activation energies for eSWIR operation mode are obtained by Arrhenius curve fitting of dark current densities at different temperatures and the non-ideality factor is found as 1.26 between 300 K and 240 K, which proves non-ideal current components originated from lattice mismatch are suppressed effectively.
Citation Formats
M. S. Gül, “Fabrication and Characterization of SWIR/eSWIR Dual-Band nBn InGaAs Focal Plane Arrays,” M.S. - Master of Science, Middle East Technical University, 2023.