Investigation on performance degradation mechanism of GaN p–i–n diode under proton irradiation

Abstract

Radiation effects of a 150 keV proton beam with various fluences on GaN-based quasi-vertical p–i–n diodes are investigated. For fundamental analysis, the electrical properties of P-GaN and N−-GaN separated from p–i–n diodes are also investigated. With the increase in the radiation-induced defect (e.g., VN and VGa) density, the carrier concentrations and mobilities of P-GaN and N−-GaN decrease significantly. Under the proton fluence of 1 × 1015 p/cm2, P-GaN has been transformed into highly resistive N-GaN, resulting in p–i–n diodes losing electrical characteristics of the PN junction. Meanwhile, the P-GaN Ohmic contact has been converted to Schottky contact. In addition, due to a large number of radiation-induced defects in P-GaN and N−-GaN, the reverse leakage current mechanism is revealed to change from space-charge-limited current conduction to Ohmic conduction.