Power diodes or transistors must be able to work in high voltage/high current use, for instance in AC/DC converters. However, in such aggressive conditions trapping effects can occur. In this work, a negative voltage stress has been applied to AlGaN/GaN Schottky barrier diodes by sweeping the bias from 0 V to ? 600 V. This voltage corresponds to the real conditions of use of the power diodes. Using deep level transient spectroscopy measurements, we demonstrated that five traps labeled E1, E2, E3, B and A with activation energies 0.4, 0.44, 0.50, 0.58 and 0.65 eV respectively, are linked to the effects of the negative bias stress. Trap E2 has been localized in the channel region and carbon impurity is expected to be involved in trap E1. We demonstrated that no significant contribution on the reduction of the sheet carrier concentration in the channel can be attributed to these deep traps. © 2017 Elsevier B.V.