Fabrication and Characteristics of Te-Se-Cd Structures

Abstract

Studies on a Te-Se-Cd sandwich structure containing a monocrystalline film of trigonal selenium were first reported at the 1967 Symposium on the Physics of Selenium and Tellurium and published soon after [1], [2]. The structures were fabricated by vacuum deposition of selenium on to a heated substrate of monocrystalline tellurium with its surface in either the (0001) basal plane or the (1010) prism plane. The device, while similar to the commercial selenium rectifier, differs from it not only in having a monocrystalline selenium layer but in having this layer much thinner, with a completely ohmic contact between the selenium and the tellurium. For rectification the selenium film thickness need only be large enough to contain the depletion layer, which amounts to less than two microns for large reverse voltages. As a consequence, a Te-Se-Cd structure can be made to give a higher current density in the forward direction above about 1 volt, where it is space charge limited [3], than the commercial rectifier with its thicker (50–100 microns) polycrystalline selenium layer.