Showing papers by "Eric R. Heller published in 1995"

Superlattice parameters for optimum absorption in inas/inxga1-xsb superlattice infrared detectors

Abstract: The linear absorption coefficient of InAs/InxGa1−xSb superlattices is optimized with respect to layer widths, indium content, substrate type and substrate orientation, interface type, and choice of buffer layers based on a model envelope‐function approach (EFA) involving the solution of a 6×6 EFA Hamiltonian (heavy, light, and conduction bands) for wave functions and subband energies. Free‐standing superlattices as well as superlattices matched to a number of substrates are considered. In general, increasing the indium mole content from 0 to 0.4 doubles the magnitude of absorption. Changing the substrate orientation from [001] to [111] significantly increases absorption in all cases studied due to the increased heavy‐hole mass and the larger InAs‐conduction‐band–InGaSb‐valence‐band offset in the [111] direction. The use of an In0.4Ga0.6Sb substrate leads to higher absorption because all the beneficial effects of strain are placed in the InAs layer, which is more sensitive to strain than is the InGaSb layer. The larger valence–conduction‐band offset for InSb than for GaAs interfaces also leads to higher absorption. The model results agree best with available data when a 100 meV InAs‐conduction‐band–GaSb‐valence‐band offset is used. Specific superlattice parameters that optimize absorption for free‐standing superlattices on GaSb at three cutoff wavelengths are proposed.