Characterization of Localized degradation in reverse-biased GaN HEMTs by scanning Transmission Electron Microscopy and Electron Holography

The AlGaN/GaN heterostructure provides the basis for the current generation of high electron mobility transistor (HEMT) devices. Due to their large band gap, high thermal conductivity and high saturation drift velocity; GaN-based devices have great potential as high-power, high-frequency devices and switches [1]. The current challenge facing these high-performance devices has been maintaining device reliability and stability. Current research is focused on identifying possible failure modes caused by defect formation arising from the inverse piezoelectric effect [2]. High electric fields combined with the piezoelectric nature of the barrier material result in very high localized stress at the gate edge, which can lead to the formation of defects and eventual device degradation [3]. This ongoing study is utilizing the phase sensitivity of electron holography to compare the two-dimensional electrostatic potential at the gate edge in stressed and unstressed devices to investigate electrical degradation caused by reverse-bias stress testing