High external quantum efficiencies have been obtained for GaP red‐emitting diodes fabricated by a single liquid‐phase epitaxy, in which Zn, O‐dopedp‐type layers were grown directly on Te‐dopedn‐type solution‐grown (SG) and liquid‐encapsulated Czochralski (LEC) substrates. For SG single‐epitaxy diodes, the quantum efficiencies (&eegr;≃6%) and the other electrical and electroluminescent characteristics are nearly identical to those observed in the previously reported double‐epitaxy diodes, demonstrating that the double‐epitaxy structure is not essential for high efficiencies. For LEC single‐epitaxy diodes, the quantum efficiencies (&eegr;≃2%) establish for the first time the present utility and future potential of LEC crystals in fabricating efficient diodes by single epitaxy.