HEMT (High Electron Mobility Transistor) are playing a key role for power and RF low noise applications. As well as the improvement of the MMIC performances, the localization of the defects linked with hot electron and the failure analysis of these devices are very challenging. To face these challenges, we have developed a complete approach, without degrading the component, based on front side failure analysis by UV electroluminescence or UV light emission. Its feasibility and efficiency have been demonstrated through two case studies. So, a specific UV microscopy technique has been developed and is presented in this paper.