Hot-carrier effects in gated AlGaN/GaN based high electron mobility transistors are studied by microwave noise temperature spectroscopy. Electron temperature profiles are measured and correlated to defect generation in the AlGaN/GaN channel interface. It is found that new defects are created at the AlGaN/GaN interface due to hot-electrons which are fairly well confined to the channel under the gated part. (C) 2012 Elsevier Ltd. All rights reserved.