Band structure calculation in type-II InAs/GaSb superlattices detector with thermal strain using an empirical tight-binding method

When the operating temperature rapidly reduces from room temperature to 77 K, the band structure of InAs/GaSb superlattices device will be affected by thermal strain. Two strain models of the InAs/GaSb superlattices device with and without substrate are designed and fabricated. The effective bandgap and cutoff wavelength of the superlattices devices were calculated using the empirical tight-binding method and compared with the experimental measurement results. The modeling calculations show that the thickness of silicon ROIC is the main factor affecting band structure. The horizontal strain component and bending strain component are selected to assess the effects of the thinning thickness of silicon ROIC, respectively. The model containing Al₂O₃ substrate and silicon ROIC thickness below 500 μm has less bandgap deviation and, therefore, is recommended. The measured PL spectrum and spectral response confirm the simulation results. By appropriate choice of the layer thicknesses, cutoff wavelength closed to the design value is achievable.