GaSb-InAs superlattice

Fig. 13.7. GaSb-InAs superlattice (a) AFM (b) UFM with periodicity of 40 nm (arrow i) and 8nm (arrow ii). The topographical image shows that the surface is very flat (RMS roughness < 0.2 nm over 1 pm2 area). Wider layers (arrow i) are barely visible whereas the finer ones (arrow ii) are not visible at all. The very fine superlattice (arrow ii) of layers only 4 nm wide is observable in the UFM image (Dinelli er a/.

L. L. Chang and L. Esaki, Eletronic properties of InAs-GaSb superlattices. Surface Science 98, 70-89 (1980). 

Here, there is no overlap between the band lineups of the materials. Type IIB structure are in fact special case of type II structure, where material B is either a small bandgap semiconductor or a semimetal. This results in little or no barrier for the holes in material A and the electrons in the material B. See Fig. 6c. The superlattices of InAs (Eg = 0.36 eV) and GaSb (Eg = 0.7 eV) are an examples of type III structure. 

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