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

► A fully transparent LED based on n-ZnO SC and p-GaN is fabricated via the direct-contact method.► The n-ZnO SC/p-GaN device shows UV/violet dual-color emission under electrically pumped.► The device presents a violet emission 400 nm and a UV emission 365 nm under forward and reverse biases.► The EL of the dual-color device displays good stability and reproducibility.

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.