The properties of heterojunctions betweenn‐ andp‐type crystalline silicon and certain threshold‐type amorphous chalcogenide films have been investigated. Low‐field and high‐fieldI‐Vcharacteristics, switching properties, and photoelectric behavior have all been studied. Devices fabricated with silicon substrates of opposite types are distinctly different; device characteristics at low voltages were found to be influenced appreciably by interface states. Short‐circuit photocurrent data imply band models which explain theI‐Vproperties in both the absence and the presence of light.