Abstract
Heterojunction photodiodes were made by epitaxial growth of CdS on GaAs substrate using the close-spaced technique, and their photoelectric properties were examined as a function of the substrate temperature. Good rectification and photovoltaic properties were obtained on n–n CdS–GaAs junctions. The junction showed Schottky-diode like photoresponse. Since the carrier concentration in the CdS layers was much larger than that in the GaAs substrate, the depletion layer between these junctions extended mainly on the GaAs side. The diffusion of Cd into the GaAs substrate affected photoelectric properties of the diodes. The technical data for the optimum growth conditions for good characteristics are presented. The quantum efficiency of 69% from photon to electron for monochromatic light of 6328 Å is obtained.