Composition dependence of the band gaps of In1−<i>x</i>Ga<i>x</i>As1−<i>y</i>P<i>y</i> quaternary solids lattice matched on InP substrates

Abstract

The In-Ga-As-P quaternary phase diagram required for the growth of lattice-matched In1−xGaxAs1−yPy layers on InP substrates has been determined experimentally at 650 °C. The liquidus isotherms were obtained by the seed-dissolution technique. The solidus iostherms were determined by electron-microprobe analysis performed on surfaces of quaternary epitaxial layers grown on Sn-doped InP (111) B substrates from quaternary saturated melts. Lattice constants of layers were measured by an x-ray-diffraction technique. The liquid-phase-epitaxy growth conditions of lattice-matched In1−xGaxAs1−yPy (0⩽x⩽0.47, 0⩽y⩽1.0) layers on InP were found from the results of the phase diagram and lattice constant measurements. Lattice-matched layers with various band gaps (from 1.34 to 0.74 eV at room temperature) were grown by using these conditions. Band gaps of the layers were determined by photoluminescence measurements at 300 and 77 K. The band gap at each temperature was found to be linearly dependent on alloy-composition parameters x and y and can be expressed as a function of composition by Eg=1.35−1.30x at 300 K and Eg=1.41−1.30x at 77 K. The energy shift between the two band gaps was constant all over the composition and was equal to 0.06 eV.