Universal tight-binding calculation for the electronic structure of the quaternary alloyIn1−xGaxAs1−yPy

Abstract

The energy band gaps and the density of states (DOS) of the quaternary alloy semiconductor ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{P}}_{y}$ lattice matched on InP and GaAs are calculated and analyzed by using the universal tight-binding (UTB) method based on a modified pseudocell (MPC). Good agreement was obtained between the calculated values and the experimental data for the lattice-matched alloy to InP, and a new band gap trend was observed for the lattice-matched alloy to GaAs. In addition, the entire composition variations of the \ensuremath{\Gamma}, $L,$ and $X$ band gaps for the ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{P}}_{y}$ alloy are obtained. The calculations suggest that the alloy ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{As}}_{1\ensuremath{-}y}{\mathrm{P}}_{y}$ in the low composition range of $(x,y)$ and lattice matched to InP can be used for efficient light emitting devices, but not for lattice matching to GaAs. The origin of band bowing is interpretated as the atomic orbital interactions through the bond alternation. The anion mixing 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 conduction band. The theoretical model is generic and applicable to various quaternary alloy systems.