Bandgap and lattice constant of GaInAsP as a function of alloy composition

Published data for the composition dependence of the room-temperature bandgap (E_g) and lattice constant (a_o) in the pseudobinary Ga_yIn_1-yAs, Ga_yIn_1-yP, GaAs_xP_l-x, and InAs_xP_l-x systems have been used to derive the following equations for the quaternary Ga_yIn_l-yAs_x P_l-x, alloys: $$begin{gathered} a_o ({AA}) = 5.87 + 0.18x - 0.42y + 0.02xy hfill E_g (eV) = 1.35 - x + 1.4y - 0.33xy - (0.758 - 0.28x)y(1 - y) hfill - (0.101 + 0.109y) x(1 - x). hfill end{gathered} $$ Available experimental data are in excellent agreement with these equations.