III-V HBT (Heterojunction Bipolar Transistor) and 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 and the failure analysis of these devices are very challenging. Active area thickness is only few nanometers, backside failure localization is mandatory because of thermal drain or metal bridge covering the front side, materials involved might be of ultimate hardness and/or high chemical sensitivity while failure mechanisms strongly differ from Si technology ones. To face these challenges, we have developed a complete approach, without degrading the component, based on backside failure analysis by electroluminescence. Its efficiency and completeness have been demonstrated through case studies.