The photoluminescence spectra of CuGaS2crystals doped with Cd or Zn vary continuously from a green emission (0.51 &mgr;) to an orange emission (∼ 0.59 &mgr;) depending upon the concentrations of Cd and Zn. The room‐temperature internal quantum efficiency is reproducibly 0.2%. The electroluminescent efficiencies of CuGaS2: CdS heterojunction LEDs fabricated by using these substrates are not appreciably higher than the best efficiencies reported earlier.