“…[1][2][3] At present, the reproducible fabrication of stable, high-quality p-type ZnO is still a challenge, which hinders the development of ZnO-based homojunction LEDs. [4][5][6][7] An alternative approach is to fabricate heterojunction devices by using other available p-type materials, such as p-GaN, p-Si, p-NiO, p-type organics etc. [8][9][10][11][12][13][14][15] Among them, GaN has been considered as the most suitable one because of its similar energy band structure and small lattice mismatch with ZnO.…”