Tailoring InAs/Ga<SUB>1-x</SUB>In<SUB>x</SUB>Sb superlattices for long-wavelength IR applications

A systematic study has been carried out on the design of long-wavelength infrared detector materials from InAs/GaSb and InAs/GaInSb supelattices with absorption energies below 250 meV, i.e. λ &gt; 5 &#181;m. The influence from layer thicknesses and alloy composition on cut-off wavelength and optical matrix element has been analysed. A three-band envelope-function model including strain effects was used to calculate conduction-band electron and valence-band light-hole states, while an effective-mass approximation was used to describe heavy-hole states. In order to achieve useful absorption coefficients, the period of such superlattices must be less than typically 20 monolayers. Calculations revealed that the absorption can be increased with almost unaffected cut-off wavelength by reducing the GaInSb thickness. The effects of including a small amount of In in the GaSb in order to reach longer wavelengths were studied. One conclusion is that although it makes longer wavelengths possible, it also makes the cut-off wavelength much more sensitive to monolayer and composition fluctuations. Copyright 1994, 1999 Academic Press