Near-white light-emitting diode from p-CuO/n-GaN heterojunction with an i-CuO electron blocking layer

Abstract

• Near-white LED based on p-CuO/i-CuO/n-GaN was realized by magnetron sputtering and annealing treatment. • CuO could be used as hole injection layer and electron blocking layer under different annealing condition. • The chromaticity coordinates and related color temperatures of the devices were about (0.2381, 0.2606) and 22,505 K. • The i-CuO layer could improve the stability of electron injection and optimize the structure of diode. White light-emitting diodes (WLEDs) have advantages of high efficiency, energy saving, and long working-life, which are ideal choice for next generation of solid-state light sources. Herein we fabricated the near-white light-emitting diode based on the structure of p-CuO/i-CuO/n-GaN heterojunction by magnetron sputtering and annealing treatment. The surface morphology, crystal quality and electrical properties of the CuO layer were investigated by X-ray diffractometer, field emission-scanning electron microscope and Hall measurement. And the influence of the CuO electron blocking layer (EBL) on the diode characteristics were discussed. The current-voltage (I-V) characteristics of those diodes revealed typical p-n junction. Compared with p-CuO/n-GaN heterjunction diode, the EL spectrum of p-CuO/i-CuO/n-GaN heterjunction diode exhibited blue shift and higher intensity. It was found that the addition of CuO EBL enhanced the stability of the diode through analyzing the I-V and EL properties of the diodes. Moreover, at the injection current of 50 mA, the chromaticity coordinates of p-CuO/n-GaN and p-CuO/i-CuO/n-GaN heterojunction diodes are about (0.2686, 0.3334) and (0.2381, 0.2606), and the color temperature are 9205 K and 22,505 K, respectively. Eventually, the EL working mechanism of the two diodes was analyzed in the aspect of the energy band diagram. This study demonstrates the possibility of p-CuO/n-GaN heterojunction with an i-CuO electron blocking layer and their potentials for applications in WLEDs.