Dx-like defects in AlGaN/GaN structures by means of noise spectroscopy

We present experimental results on the noise of Au/Al_0.3Ga_0.7N/GaN-based structures. The layers are as-grown n-type and were fabricated using metalorganic chemical vapor deposition. We find that the low-frequency part of the spectrum is dominated by the 1/f noise. A generation-recombination component of the noise is observed in the annealed samples. It originates from a local center present in the AlGaN layer in the vicinity of the GaN layer. It has a large capture energy barrier and disappears from the noise spectrum after illumination which suggests that it has a DX-like nature. This center may be partially responsible for the persistent photoconductivity and the collapse of the dc drain current observed in AlGaN/GaN heterostructures.