Abstract
Heterodiodes have been prepared by the growth of epitaxial n‐type CdS films from the component vapors on p‐type CuGaS2 substrates. In dc operation at 77°K, green light is emitted with an external quantum efficiency of 0.1%. For pulsed operation at room temperature, the efficiency is [inverted lazy s]0.001% . The near‐band‐gap radiation results from electron injection into a semi‐insulating CuGaS2 region near the CdS/CuGaS2 interface. This region also controls the forward current of the diodes.