ZnS blue-light-emitting diodes with an external quantum efficiency of 5×10−4

Abstract

ZnS diodes emitting a stable and bright blue light with forward biases above 5 V are investigated. The external quantum efficiency for the diode is as high as 5×10−4 at room temperature. The presence of a thin high-resistivity ZnS layer on the low-resistivity ZnS is essential for the present diode. The fairly high efficiency is accounted for by a relevant mechanism of the donor-acceptor–pair emission.