Gallium vacancies related yellow luminescence in N-face GaN epitaxial film

► Yellow luminescence in N-face n-type GaN was characterized. ► Outstanding increase of yellow luminescence in N-face GaN was observed after KOH etching. ► Correlation between the intensity of the YL and the concentration of Ga vacancies at the surface of KOH-etched n-face GaN was derived. ► Direct evidence shows that the yellow luminescence in n-type GaN is related to the Ga vacancies.