Effect of Interfaces and the Spin-Orbit Band on the Band Gaps of InAs/GaSb Superlattices Beyond the Standard Envelope-Function Approximation
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SURVIVABILITY AND SENSOR MATERIALS DIV/HARDENED MATERIALS
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We developed a modified 8x8 envelope-function approximation EFA formalism for the noncommon-atom NCA superlattices SLs, incorporating the effect of anisotropic and other interface IF interactions that go beyond the standard EFA. The boundary condition in the presence of IF interactions are used to set up a secular equation including a transfer matrix derivation whose physical transparency makes possible a number of valuable insights possibility of IF bound states, analytic solutions, indirect gaps, etc.. We show that the heavy-hole-spin-orbit IF coupling is very important due to the IF localization of the SO wave function components and the ability of the IF potential to potentially bind a hole at the IFs, all of which pose convergence problems for perturbative solutions. With two adjustable parameter for the two possible IFs, we find a very good agreement between experiment and theory for the band gaps of several sets of very long-infrared and midinfrared InAsGaSb SLs grown at several laboratories and by us. The band gaps as a function of GaSb and InAs widths are explained in terms of variations of the HH and conduction C bandwidths.
- Numerical Mathematics