The indium desorption rates from InGaAs and InAlAs grown on InP substrates have been measured by wedge transmission electron microscopy as a function of the growth temperature. Desorption becomes significant at 545-degrees-C for both materials. No automatching effects could be observed under the growth conditions of the experiment. The bandgap of In(y)Al1-yAs has been measured at 77 K as a function of the indium content. The composition and the strain have been measured by four-crystal high resolution X-ray diffraction with symmetrical (004) and assymmetrical (115 +/-) Bragg reflections. The intrinsic bandgap follows the relation E(g)(y) = 2.774 - 2.411 y and the strained material the relation E(gs)(y) = 0.671 + 5.236y-6.929y2.