InAs layers and InAs/GaSb type II superlattices (SLs) were grown on (001) GaAs substrates by metalorganic chemical vapor deposition. A thin low-temperature GaSb nucleation layer and a thicker high-temperature metamorphic GaSb buffer layer were introduced before the growth of InAs or the SLs. By optimizing the growth temperature, the interface gas switching and the growth rate, morphology, and structural properties of the grown structures are significantly improved. In some cases, nanopipes are found in these structures. Morphology studies of the InAs heteroepitaxial layers show that (1) the diameter of these nanopipes decreases with the growth temperature; (2) nanopipes are nucleated from the interface of GaSb/InAs; and (3) the density of nanopipes depends on the passivation of GaSb surface before the growth of the InAs. In growing InAs/GaSb SLs, we show that the growth rate of GaSb has a strong effect on the morphology and that the unintentional interfacial InSb layer formed at the InAs/GaSb interfaces is the origin of the nanopipes. Through the optimization of the growth parameters, high-quality 100-period SLs without nanopipes and with good optical absorption in 3–8 μm infrared region have been realized.