A study of the interface and the related electronic properties in n-Al0.35Ga0.65N/GaN heterostructure

The interface and the related electronic properties in n-Al0.35Ga0.65N/GaN heterostructure were studied non-destructively by the spectral and transient photovoltage (PV) technique. A defect level as recombination center was observed in the buffer layer of GaN at the side close to the substrate. It was found that the GaN layer of 3 μm was completely depleted owing to the formation of two-dimensional electron gas. When the sample was illuminated at the front or the back side, with a laser radiation of 355 nm, the electron-hole pairs were generated in GaN layer and then separated there. By the action of the electric field in GaN layer, the holes moved to the substrate, while the electrons moved to the AlGaN/GaN interface. In the PV transients under the front illumination, a fast and a slow component, related to the initiative separation of the electron-hole pairs and the drift of the resultant holes, respectively, were observed. At higher illumination intensities, the bimolecular recombination happened to the fast component, while in that period of time it did not to the slow one owing to the long separation distance between the electrons and the holes.