Mechanical stress effects on electrical breakdown of freestanding GaN thin films

Gallium Nitride (GaN) devices are intended to operate at high temperature and mechanical stress conditions, rendering reliability a major concern. To investigate the effects of temperature and stress on electrical breakdown they were applied individually and simultaneously, on free standing epitaxially grown GaN specimens after release from the growth substrate. Both temperature and mechanical stress were seen to degrade the material by decreasing the breakdown voltage. Up to 60% decrease was observed at around 870 MPa. It is hypothesized that stress-generated defects climb to the free surfaces, creating localized leakage current instability or 'ringing' effects. This study also captures the synergy of temperature and stress, which can be translated to breakdown of buffer layers in GaN devices or in designing harsh environment sensors.