UNIVERSAL TIGHT-BINDING CALCULATION FOR THE ELECTRONIC-STRUCTURE OF THE QUATERNARY ALLOY IN1-XGAXAS1-YPY

The energy band gaps and the density of states (DOS) of the qunternary alloy semiconductor In1-xGaxAs1-yPy lattice matched on InP and GaAs a re calculated and analyzed by using the universal tight-binding (UTB) method based on a modified pseudocell (MPC). Good agreement was obtain ed between the calculated values and the experimental data for the lat tice-matched alloy to InP, and a new band gap trend was observed for t he lattice-matched alloy to GaAs. In addition, the entire composition variations of the Gamma, L, and X band gaps for the In1-xGaxAs1-yPy al loy are obtained. The calculations suggest that the alloy In1-xGaxAs1- yPy in the low composition range of (x,p) and lattice matched to InP c an be used for efficient light emitting devices, but not for lattice m atching to GaAs. The origin of band bowing is interpretated as the ato mic orbital interactions through the bond alternation. The anion mixin g affects on the shift of the DOS peak position and the cation mixing plays a dominant role on the change of the DOS peak intensity in the c onduction band. The theoretical model is generic and applicable to var ious quaternary alloy systems.