Rediscovery of the Role of the i-Layer in n-ZnO/SiO2/p-GaN Through Observations from Both the ZnO and GaN Sides

Ultraviolet (UV)-emitting n-ZnO/SiO2/p-GaN devices were fabricated by metalorganic chemical vapor deposition. Electroluminescence spectra of the devices were measured from both the n-ZnO and p-GaN sides. It was found that a narrow emission peak centered at ∼391.3 nm was observed from the front side, while three peaks (372 nm, 380 nm, and 390 nm) emerged in the case of testing from the GaN side. To interpret this notable difference, a theoretical mechanism is proposed based on carrier accumulation and injection under forward bias voltage.