Novel Method for Accelerated Thermal Cycling of Gallium Nitride Power Devices to Perform Reliability Assessment

Gallium Nitride (GaN) FET devices are becoming very popular in the power industry due to their fast switching characteristics and the benefits associated with very high switching frequency operation. The device degradation process of the GaN plays vital role in characterizing the reliability. Thermal cycling is one of the accelerated reliability assessment processes that involves heating the GaN FET device by passing current up to a maximum temperature and cooling it either naturally or forcefully. Precise identification of the device junction temperature is crucial to avoid thermal runaway during cycling process. Fast thermal cycling using conventional junction temperature identification methods leads to thermal runaway of GaN FET device, which delays the reliability assessment. Hence in this paper, a novel approach using on-state-resistance ${(R_{DSon})}$ based junction-temperature estimation is proposed to avoid thermal runaway of the devices and achieve accelerated degradation process. To evaluate the proposed technique, GaN FET devices are power cycled with maximum ${R_{DSon}}$ limit as well as with temperature limitation. The experimental results validate that ${R_{DSon}}$ based cycling method can avoid the thermal runaway and reduces degradation assessment process time.