GaN MSM UV photodetector were fabricated on n-GaN epitaxial layer. The effect of room temperature ⁶⁰Co γ-radiation at very low dose rate (0.0001 rad(Si)/s) on the electric current of photodetector was studied. In contrast to earlier observations, by increasing the gamma dose, an initial increasing of the dark current followed by the gradual decrease has been observed. The abnormal behavior of the voltage-current characteristic of the photodetector can be explained by considering the carriers transfer mechanism in localized states, which is very common in III-Nitride semiconductors. The results presented here are found to be important in understanding the mechanism of interaction of  ⁶⁰Co γ-irradiation with n-GaN epilayer.

Keywords: photodetector, GaN, gamma, dark current.

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