Charge trapping centres in γ-irradiated Gallium Nitride grown by MOCVD

Deep-level transient capacitance measurements (DLTS) were performed on Schottky diodes fabricated on undoped MOCVD-grown GaN epilayers before and after exposure to different doses of ⁶⁰Co gamma-irradiation. The DLTS measurements were performed from 77 to 300 K, and the samples exposed to accumulated doses of 200, 500 and 1000 krad(Si). Three deep-levels were found in the sample prior to irradiation with thermal activation energies of 241 ± 5, 294 ± 32 and 575 ± 2 meV. Our measurements indicate that for low doses (≤ 1Mrad(Si)) no new traps have been induced, and that the traps present in the unirradiated material do not experience any significant change in their characteristics. In contrast, a recent report on ⁶⁰Co γ-irradiated magnetron-sputtered GaN indicates an increase in the concentrations of deep-levels with thermal activation energies of 590 and 820 meV for accumulated doses of 1 Mrad and above.