ELECTRONIC-STRUCTURE, ABSORPTION-COEFFICIENT, AND AUGER RATE IN HGCDTE AND THALLIUM-BASED ALLOYS

The band structures, absorption coefficients, and Auger recombination rates in narrow-gap alloys HgCdTe, InTlP, InTlAs, and InTlSb in the zi nc blende structure, along with those of GaAs, are calculated using a hybrid pseudopotential and tight-binding method. The composition-depen dent band gaps of the thallium-based alloys are reported along with th ose of several other semiconductor alloys. Within 50 meV from the abso rption edge, the absorption coefficient of InxTl1-xP is found to have about the same magnitude as that of HgxCd1-xTe and GaAs, while that of InxTl1-xAs and InxTl1-xSb is much smaller. In agreement with previous theories, the calculated Auger lifetimes in Hg0.78Cd0.22Te with unit or k.p overlap agree very well with experiments. Among the thallium al loys studied, the Auger lifetimes are longest in In0.33Tl0.67P, but st ill shorter than those in Hg0.78Cd0.22Te by an order of magnitude. In addition, realistic overlaps produce lifetimes one to two orders of ma gnitude larger than those observed.