The effects of high-energy uranium ion irradiation on Au/n-GaN Schottky diodes

The I–V and C–V characteristics of Au/n-GaN Schottky diodes irradiated with 290-MeV 238U32+ ions are presented. The U ions can penetrate the n-type GaN epi-layer with a thickness about 3 μm grown on the c-plane of a sapphire substrate using the MOCVD technique, leaving a purely electronic energy deposition. The Au/n-GaN Schottky diodes were irradiated to successively increasing fluences from 1 × 109 to 5 × 1011 ions cm−2. The measured I–V curves show that the height of the Schottky barrier decreases after irradiation and that the Schottky barrier almost disappears when the ion fluence reaches 5 × 1010 ions cm−2. Meanwhile, the irradiation increases the series resistance. The C–V curves show that the capacitance drops sharply when the ion fluence reaches 5 × 1010 ions cm−2. The dielectric constant also decreases following the irradiation. The changes of the electrical properties are ascribed to the neutralization of the donor-like surface state and the acceptor-like surface state due to the migration of Au atoms at the interface of Au/n-GaN under energetic U ions irradiations.