Anticrossing semiconducting band gap in nominally semimetallic InAs/GaSb superlattices

While $(\mathrm{InAs}{)}_n/(\mathrm{GaSb}{)}_n$ (001) superlattices are semiconducting for $n<\mathrm{}{n}_c\approx 28\mathrm{ML},$ for $n>\mathrm{}{n}_c$ the InAs electron level $e_{\mathrm{InAs}}$ is below the GaSb hole level $h_{\mathrm{GaSb}},$ so the system is converted to a nominal semimetal. At nonzero in-plane wave vectors $\left({\mathbf{k}}_{\Vert }\ne 0\right),$ however, the wave functions $e_{\mathrm{InAs}}$ and $h_{\mathrm{GaSb}}$ have the same symmetry, so they anticross. This opens up a “hybridization gap” at some ${\mathbf{k}}_{\Vert }={\mathbf{k}}_{\Vert }^{*}.$ Using a pseudopotential plane-wave approach as well as a (pseudopotential fit) eight-band $\mathbf{k}\cdot \mathbf{p}$ approach, we predict the hybridization gap and its properties such as wave-function localization and out-of-plane dispersion. We find that recent model calculations underestimate this gap severely.