Electroreflectance study of (AlxGa1-x)(0.5)In0.5P alloys

Electroreflectance spectroscopy has been applied to the study of (AlxGa1-x)(0.5)In0.5P quaternary systems lattice-matched to GaAs. The measurements are made at room temperature in the photon-energy range of 1.7-5.8 eV. The composition dependence of the E(0), E(0) + Delta(0), E(1), E(2) and E(2) + delta gaps has been determined. The lowest direct band gap is found to be given by E(0)(x) = 1.90 + 0.57x + 0.11 x 2 eV. The E(0) + Delta(0), and E(1) gaps are written as similar quadratic equations. On the other hand, the variation of the E(2) and E(2) + delta gaps is found to be approximately linear. The lowest direct-to-indirect gap crossover is also estimated to occur at x similar to 0.63.