Photoreflectance‐derived band‐gap parameters as a function of temperature for InGaAs and InAlAs lattice matched to InP are reported. The experiment was performed on a set of samples of various compositions (and strains) yielding greater reliability and ensuring self‐consistency. For InGaAs, fits to the Varshni equation gaveE0(T=0 K)=803 meV, &agr;=4.0×10−4eV K−1, and &bgr;=226 K. For InAlAs,E0(T=0 K)=1.541 eV, &agr;=4.7×10−4eV K−1, &bgr;=149 K, and &Dgr;0=338 meV.