  A holistic computational analysis is developed to calculate the quantum
efficiency of InAs/GaSb superlattice-based photodetectors. Starting with the
electronic band characteristics computed by taking the InSb/GaAs at the
interface using the 8-band k.p approach, we demonstrate the impact of InAs and
GaSb widths on the bandgap, carrier concentration, and the oscillator strength
for type-II superlattice absorbers. Subsequently, the alteration of these
characteristics due to the extra AlSb layer in the M superlattice absorber is
investigated. Extending our models for determining TE- and TM-polarized optical
absorption, our calculations reveal that the TE-polarized absorption shows a
substantial influence near the conduction-heavy hole band transition energy,
which eventually diminishes, owing to the dominant TM-contribution due to the
conduction-light hole band transition. Extending our analysis to the dark
currents, we focus mainly on Schokley-Read-Hall recombination and radiative
recombination at lower temperatures, and show that Schokley-Read-Hall dominates
at low-level injection. We show that short-wavelength and mid-wavelength M
superlattice structures exhibit higher quantum efficiency than the
corresponding same bandgap type-II superlattice with the lower diffusion dark
current. Further, we analyze the density of states blocked by the barrier;
crucial for XBp photodetector after absorber examination. Our work thus sets a
stage for a holistic and predictive theory aided analysis of the type-II
superlattice absorbers, from the atomistic interfacial details all the way to
the dark currents and absorption spectra.
