Electrical Characterization of Defects Introduced In n-GaN During High Energy Proton and He-Ion Irradiation

We report on the electrical properties of defects as determined by deep level transient spectroscopy (DLTS) introduced in epitaxially grown n-GaN by 2.0 MeV protons and 5.4 MeV He-ions. After He-ion bombardment three electron traps ER3 (E c − 0.196 eV), ER4 (E c − 0.78 eV), and ER5 (E c − 0.95 eV) were introduced uniformly in the region profiled by DLTS with introduction rates of 3270 ± 200, 1510 ± 300, and 3030 ± 500 cm− 1 respectively. Capture cross section measurements revealed that the electron capture kinetics of ER5 is similar to that of a line defect. A defect with similar electronic properties as ER3 is observed after 2.0 MeV proton irradiation. The emission rate of ER3 depends on the electric field strength in the space-charge region. This emission rate is modelled according to the Poole-Frenkel distortion of a square well with a radius of 20 ± 2 Å or alternatively, a Gaussian well with a characteristic width of 6.0 ± 1 Å. Hence, we conclude that ER1 is a point defect which appears to have an acceptor like character. Two additional electron traps, ER1 (E c −0.13 eV) and ER2 (E c − 0.16eV) with introduction rates of 30 ± 10 and 600 ± 100 cm −1 not thusfar observed after electron or He-ion bombardment were observed after proton irradiation.