ABSTRACT
Type-II InAs/GaSb superlattices (SLs) are the broken gap periodic heterostructures, which were invented in the early 1970s by Sai-Halasz, Tsu, and Esaki.1 This type of structures is very specic because of the bandgap arrangement of the SL constituents (i.e., InAs and GaSb materials) (Figure 615a). The oddity of the arrangement is that the minimum of the conduction band (CB) in InAs layers lies below the maximum of the valence band (VB) in GaSb layers. Special features of such structures make them very interesting for various civil and military optoelectronic applications: mid-and long-wavelength infrared (i.e., MWIR and LWIR) detectors,2-22 dual-color detectors and focal plane arrays (FPAs),23-29 and mid-infrared (IR)-emitting diodes and interband cascade lasers (ICLs).6,30-45
In InAs/GaSb SLs, holes and electrons are spatially separated-holes are localized in GaSb and electrons in InAs layers. However, if the layers are thin enough, the wave functions of holes and electrons can overlap strong enough to ensure the absorption of light incident on the SL structure. Effective bandgap of the SL (see Figure 615b) can be tailored by the proper choice of thickness of InAs and GaSb layers. InAs/ GaSb SL detectors can operate at room temperature and exhibit very good properties in comparison with other IR detectors, for example, the mercury-cadmium-telluride ones.
