An AlGaN/GaN HEMT was irradiated with 5 MeV protons at a dose up to 2 x 10(15)/cm(2). Photoluminescence spectra measured at 5 K indicated that GaN lattice was severely damaged by collisions with high energy protons although distinct near band-edge features were still observable. An I(DS)-V(DS) measurement showed that the current level was decreased by 43% after proton irradiation, and an I(GS)-V(GS) measurement suggested that damage at the metal-contact/AlGaN interface was minimal. Transistor operation was found to be resistant to proton irradiation, which was partially attributed to a self-healing mechanism in proximity to the AlGaN/GaN interface. Published by Elsevier B.V.