Photocurrent measurements are shown to provide a convenient technique for determining the nitrogen concentration in the active region of GaP diodes designed for green light emission. The strength of the photocurrent peak at theA‐line energy can be correlated semiquantitatively with the diode efficiency in devices which differ only in their nitrogen content. Room‐temperature photocurrent measurements of Schottky barrier diodes formed by gold evaporation on epitaxial material can be similarly used for determining the relative nitrogen concentration.