Ga1−xAlxAs light‐emitting diode structures have been grown on GaP substrates by the liquid‐phase‐epitaxial method. In spite of the large differences in lattice constants and thermal‐expansion coefficients, room‐temperature efficiencies up to 5.5% in air have been observed for a peak emission of 8500 Å. Previously, in order to achieve high external efficiencies it was necessary to grow thick Ga1−xAlxAs layers on GaAs substrates and then remove the substrate. However, using undoped GaP substrates, which are transparent to the infrared and red portions of the spectrum, thin structures of Ga1−xAlxAs with large external efficiencies can now be made.