Tunable energy gaps and mid-infrared optical properties in InAs/GaSb type-II superlattices

We investigate on the infrared (IR) optoelectronic properties in short-period InAs/GaSb type-II superlattices (SLs) by a modified eight-band K . P model. The electronic mini band structures for such SLs are evaluated by the modified eight-band K . P model, incorporating the microscopic interface effect. We find that with varying the values around 20/25 A for the InAs/GaSb layer widths, the tunable mid-IR bandgaps can be achieved effectively. The SL bandgap from 275 to 346 meV can be achieved by decreasing the InAs layer thickness from 23 to 17 A at a fixed GaSb layer thickness of 24 A, or from 254 to 313 meV by increasing the GaSb layer thickness from 18 to 27 A at a fixed InAs layer thickness of 21 A. Correspondingly the optical absorptions in such systems can be tuned evidently. Our theoretical results are in good agreement with experimental data over a series of SL samples. This study confirms further that short-period InAs/GaSb type-II SLs are of great importance for IR applications.