Effect of microscopic interface asymmetry on optical properties of short-period InAs/GaSb type-II superlattices

We theoretically investigate the effect of microscopic interface asymmetry (MIA) on the optical properties of short-period InAs/GaSb type-II superlattices (SLs) which can serve for the mid-infrared (mid-IR) detection. To calculate the band structures of such SLs, we use a modified eight-band Kane model which includes the MIA effect. With the band structures, we can evaluate the optical matrix elements and joint density of states for the corresponding SL systems. Based on these obtained results, we employ the Boltzmann equation approach to calculate the optical absorption coefficients for the corresponding SL systems. Theoretical calculations demonstrate that the MIA effect can greatly influence the electronic and optical properties of short-period InAs/GaSb type-II SLs. For the band structures, we find that the MIA effect causes strong interactions between different SL subbands and creates large spin splittings of these subbands. For the optical properties, the MIA effect activates the forbidden optical transition channels for TM polarization, enhances the absorption strength considerably and induces remarkable red-shifts for both transverse electric (TE) and transverse magnetic (TM) polarizations, where TE and TM refer to light polarizations along the in-plane and growth directions of SL structure. Different absorption features for TE and TM polarizations are well manifested by corresponding optical matrix elements. Moreover, in conjunction with recent experiment, we calculate the polarization-dependent absorption spectra for mid-IR InAs/GaSb type-II SLs. Our theoretical results can explain those observed experimentally. The present work sheds the significant importance of MIA effect in short-period InAs/GaSb type-II SLs. - Highlights: • Optical properties of InAs/GaSb superlattices (SLs) are studied theoretically. • The microscopic interface asymmetry (MIA) effect is considered for such SLs. • The MIA effect influences the optical properties of such SLs significantly