Electrical forming action in Te-Se-Cd structures

Improved techniques have been developed for the fabrication of rectifying Te-Se-Cd sandwich structures, where the selenium is present as a thin monocrystalline film. The electrical forming action, which has been used for many years to improve the performance of selenium rectifiers, has been investigated in these simple structures. Analysis of capacitance-voltage characteristics indicates that the electrical forming process is a progressive reduction in the concentration of acceptors in the selenium within a region of about half a micrometer from the junction. Scanning-electron microscopy has failed to reveal CdSe at the Cd-Se interface after electrical forming, although this compound is found after thermal forming. The studies indicate that, contrary to previously held views, CdSe is not necessary for the rectification and that the device involves essentially a Schottky junction rather than a heterojunction of n-CdSe and p-Se.