Injection Electroluminescence in ZnS and ZnSe

Abstract

Injection electroluminescence has been observed in Cu₂S‐ZnS and Cu₂Se‐ZnSe heterojunctions. The light emission occurs through hole injection from the p‐type Cu chalcogenide into n‐type ZnS or ZnSe. At room temperature the light emission from the Cu₂S‐ZnS and the Cu₂Se‐ZnSe junctions originates at the Cu or self‐activated luminescence centers. At 77°K the Cu₂Se‐ZnSe diodes exhibit emission bands peaking at 1.96, 2.07, 2.36, and 2.68 eV. The dominance of any one of these bands over the others can be achieved by appropriate preparative techniques. In the diodes emitting predominantly in the 2.36‐eV band the light intensity varies approximately as the $\frac{3}{2}$ power of current. The lowest voltage threshold observed for visible light emission is 1.5 V. Both the luminescence and the electrical characteristics of the prepared diodes are in accord with a tentative model for the band structure of Cu chalcogenide‐II‐VI compound heterojunctions. The particular model for the Cu₂Se‐ZnSe diodes is presented and discussed in detail.