Long Minority Carrier Lifetimes in InAs/InAsSb Type-II Superlattices*

Three unintentionally doped MWIR InAs/InAsSb type-II superlattices (T2SLs) were designed and grown to have 15 {\%} Sb content in their alloy layers. The individual layer thicknesses of InAs and InAsSb are systematically altered in configurations of 174/218, 87/109, and 65/82 ({\AA}/{\AA}) while the total absorber thickness is nominally 4 $\mu $m and the bandgap is approximately 5.2 $\mu $m for all the samples. A time- and temperature- dependent differential-transmission technique was used to evaluate the carrier lifetime of each of the samples. Significantly long minority carrier (MC) lifetimes of \textasciitilde 14 $\mu $s and \textasciitilde 19 $\mu $s were obtained for the sample with 174 {\AA} /218 {\AA} InAs/InAsSb layer ratio at the temperatures of 77 K and 125 K, respectively. The defect energy levels of the InAs/InAsSb T2SLs reported here are determined to be \textasciitilde 300 \textpm 25 meV relative to InAs valance band edge strained to GaSb. Additionally, the electron dominated Auger coefficients, C$_{\mathrm{n,\thinspace }}$are obtained from the excess carrier density and temperature dependent recombination rate data. These coefficients are found to increase with decreasing individual layer thickness values from 3.4 to 29.9 x 10$^{\mathrm{-27\thinspace }}$cm$^{\mathrm{6}}$/s at 77 K.