Heterostructure engineering in Type II InAs/GaSb strained layer superlattices

The background carrier concentration is an important factor in the performance of detectors. We have investigated the effect of a variable background doping concentration in the absorber region of an nBn type-II InAs/GaSb superlattice infrared detector. The doping concentrations were 5 x 1016 cm-3 (non-intentionally doped, n.i.d.), 1.4 x 1017 cm-3, 4.0 x 1017 cm-3, and 3.5 x 1018 cm-3. The specific detectivity of the detectors was found to dramatically decrease as the doping concentration was increased. This was caused by an increase in dark current density which is attributed to the presence of a quantum well (QW) formed in the valence band. This QW allowed for enhanced electron-hole recombination at higher doping concentrations. Consequently the n.i.d. device demonstrated the best performance with a zero bias specific detectivity (D*) equal to 1.2 x 1011 Jones at 77 K. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)