Ultraviolet/violet dual-color electroluminescence based on n-ZnO single crystal/p-GaN direct-contact light-emitting diode

We have fabricated a fully transparent ultraviolet (UV)/violet dual-color electroluminescence (EL) device based on n-ZnO single crystal and p-GaN via a simple direct-contact method. The device presents dual-color EL under forward and reverse biases—an intense violet emission centered at 400 nm from ZnO and a sharp UV emission peaked at 365 nm from GaN, respectively. The reason for dual color emissions is proposed in terms of the energy band theory and the transmission spectra of ZnO single crystal and p-GaN.